Removing saved data

Apps are forever associated with the AppleID from which the App was originally purchased. Apps can only be re-installed or updated, from the App Store, using the AppleID that was used to originally purchase the App.

If the AppleIDs differ, reinstallation or update of the affected App is not possible - and it is this situation in which you appear to find yourself.

If the iPad is Activation Locked, you’ll need the AppleID and Password that was previously used to activate the iPad.

Assuming that you have full access to the iPad - and know the necessary AppleID Password, you can remove the Activation Lock relatively easily:

Settings > [Name / AppleID] > Find My > Find My iPad > Find My iPad - set to OFF; you’ll be challenged for the AppleID Password

If you are attempting to properly prepare the iPad for reuse, the most effective method is to follow this procedure:

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

This process will completely erase the iPad, remove the Activation Lock and reset - after which you’ll be able to set-up afresh as a new iPad.

If you have transferred data and settings from old to new iPad using QuickStart, or restored from a Backup associated with the previous iPad, you will have literally transferred everything from old to new - and will have an iPad that is effectively not yours. Starting again from scratch is recommended.