Hi Kierm, Welcome to Apple Support Communities. I understand that you're trying to remove your Apple ID from your old iPad but are unable to so since you didn’t sign out on that device prior to changing the email address associated with that Apple ID.

Updated 3 Effective Methods to Remove Apple ID from iPhone How to Remove Apple ID from iPhone/iPad /Apple Watch Via Apple Service-[Free] Of course, when … How to Remove Your Credit Card on iPhone and iPad Jul 01, 2020

Step 3: Before starting to remove Apple ID from the iPad, we should notice that we will erase all data in iPad after removing Apple ID from the iPad, so it's better to backup iPad data to computer. And you should make sure the connection during the whole process of erasing Apple ID from iPad.

How to Remove Apple ID from iPad - EelPhone Step 3: Before starting to remove Apple ID from the iPad, we should notice that we will erase all data in iPad after removing Apple ID from the iPad, so it's better to backup iPad data to computer. And you should make sure the connection during the whole process of erasing Apple ID from iPad. How To Remove Your Apple ID From Your iPad? - TecHLecToR How Can I Remove My Apple ID From My iPad? Open the Settings app and click on your name or image at the top-left of the display. Click “iTunes & App Store.” Click the Apple ID tab at the top of the display. Click “View Apple ID” in the popup window and, if asked, type your password.

How to Delete or Deactivate Your Apple ID Account and Data

How to Remove Apple ID from iPad & Remove Apple ID from iPhone Oct 10, 2017 How to remove a previous owner’s Apple ID from a used How to remove a previous owner’s Apple ID from a used iPhone, iPad, or iPod touch If you buy a used iOS device, make sure the previous owner has deactivated Activation Lock.