How do you get your sign in code if you can't get inot you email to retrive ot

Presumably, you need the verification code to complete your AppleID sign-in on your “as-yet untrusted” iPad.

If you have another Trusted Device, you can receive - or generate - the code on it.

If not, you need to receive it thru one of your Trusted Numbers.

If none of those options are available, you’ll end-up needing to use Account Recovery.

See more detail of ALL options available to you here:

Get a verification code and sign in with two-factor authentication - Apple Support

If you'e asking about two factor authentication, they won't come to your email, it's be displayed in a pop up panel.