Want to log into an old ipad but the email it’s

Does not matter. The associated Apple ID never stops working even the email address no longer exists. As long as you remember the password for the Apple ID, which may or may not be the same as the password for the email accounr, you should be able to access the Apple ID and as such access the iPad.

If you no longer remember the password for the Apple ID, and the email no longer functions, then you'll need to work with iTunes Account Security team to regain access to it, and update the email address to a new working one once you can access it: iTunes Support - Contact Us - Official Apple Support

Once acess to the Apple ID has been restored, you can access the iPad.