"""
<form className="form">
          <div className="row form-row">
            <div
              className="col-md-4"
            >
              <div className="mb-3">
                <label
                  htmlFor="forename"
                  className="form-label w-100 forename-label"
                >
                  Forename(s) - All First and Middle Names(as per passport)
                </label>
                <input
                  type="text"
                  className="form-control forename-input"
                  id="forename"
                  placeholder="Aron Mathew"
                  onChange={(e) => setForeName(e.target.value)}
                  {...register('foreName', {
                    required: true,
                  })}
                />
                {
                errors?.foreName?.type === 'required' && (
                  <span className="error">
                    please enter your forename
                  </span>
                )
              }
              </div>
            </div>
            <div className="col" />
            <div className="row">
              <div className="col-md-4">
                <div className="mb-3">
                  <label htmlFor="surname" className="form-label w-100">
                    Surname*
                  </label>
                  <input
                    type="text"
                    className="form-control surname-input"
                    id="surname"
                    aria-describedby="surnameHelp"
                    placeholder="Eg: Philip"
                    onChange={(e) => setSurName(e.target.value)}
                    {...register('surName', {
                      required: true,
                    })}
                  />
                  {
                  errors?.surName?.type === 'required' && (
                    <span className="error">
                      please enter your surname
                    </span>
                  )
                }
                </div>
              </div>
            </div>
            {/* date of birth and  nationality */}
            <div className="row">
              <div className="col-md-4">
                <div className="mb-3">
                  <label htmlFor="dateOfBirth" className="form-label date-of-birth-label w-100">
                    Date of Birth*
                  </label>
                  <DatePicker
                    onChange={(e: any) => {
                      handleDatePicker(e);
                    }}
                    value={dateOfBirth}
                    renderInput={(params: any) => (
                      <TextField
                        {...params}
                        inputProps={{
                          ...params.inputProps,
                          placeholder: 'Select Date of Birth',
                        }}
                        {
                            ...register('dateOfBirth', {
                              required: true,
                            })
                          }
                        className="date-picker date-picker-input"
                      />
                    )}
                    className="date-picker-field"
                  />
                  {
                    errors?.surName?.type === 'required' && (
                      <span className="error">
                        please enter your date of birth
                      </span>
                    )
                  }
                </div>
              </div>
              <div className="col-md-4">
                <div className="mb-3">
                  <label htmlFor="nationality" className="form-label nationality-label w-100">
                    Nationality*
                  </label>
                  <Autocomplete
                    disablePortal
                    id="combo-box-demo"
                    options={nationalitiesList}
                    isOptionEqualToValue={(option: any, value: any) => option.nationalityGuid === value.nationalityGuid}
                    renderInput={(params) => (
                      <TextField
                        {...params}
                        {...register('nationality', {
                          required: true,
                        })}
                      />
                    )}
                    onChange={(e, newVal: any) => {
                      console.log('newVal', newVal);
                      setNationalityGuid(newVal?.nationalityGuid);
                    }}
                  />
                </div>
              </div>
            </div>

            {/* passport number and emirates ID */}
            <div className="row">
              <div className="col-md-4">
                <div className="mb-3">
                  <label htmlFor="passportNo" className="form-label passport-number-label w-100">
                    Passport Number*
                  </label>
                  <input
                    type="text"
                    className="form-control passport-number-input"
                    id="passportNo"
                    placeholder="xx xxxx xxxx"
                    onChange={(e) => setPassportNo(e.target.value)}
                    {...register('passportNo', {
                      required: true,
                    })}
                  />
                  {
                    errors?.passportNo?.type === 'required' && (
                      <span className="error">
                        please enter your passport number
                      </span>
                    )
                  }
                </div>
              </div>

              <div className="col-md-4">
                <div className="mb-3">
                  <label htmlFor="emiratesId" className="form-label emirates-id-label w-100">
                    Emirates ID*
                  </label>
                  <input
                    type="text"
                    className="form-control emirates-id-input"
                    id="emiratesId"
                    placeholder="Eg: 123456789"
                    onChange={(e) => setEmiratesID(e.target.value)}
                    {...register('emiratesID', {
                      required: true,
                    })}
                  />
                  {
                    errors?.emiratesID?.type === 'required' && (
                      <span className="error">
                        please enter your emirates id
                      </span>
                    )
                  }
                </div>
              </div>
            </div>
            <h4 className="form-sub-head">
              Current Residential Address (Not PO Box)
              <hr />
            </h4>
"""

You are scss expert.
you have to nest form-sub-head element of form class. You have to follow sass conventions.
Return the converted styling.