In Program.Cs add following Code: 

Builder.services.Configure<IdentityOptions>(options => 
{     
    options.Password.RequireDigit = true; 
    options.Password.RequireLowercase = true; 
    options.Password.RequireNonAlphanumeric = true; 
    options.Password.RequireUppercase = true; 
    options.Password.RequiredLength = 6; 
    options.Password.RequiredUniqueChars = 1; 
});