If you have updated your AppleID account to reflect a change of email address, you’ll need to follow the post-update actions detailed here:
https://support.apple.com/en-us/HT204071
This of course assumes that you have done the right thing and updated your existing AppleID account with a new email address - and not made the fundamental mistake of creating an entirely new AppleID.
If you have an iPad2, you might wish to consider that it cannot be updated beyond iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular). Apple formally ended update support for these devices in September 2016. iPad2 cannot be updated to iOS 10 or later versions, as the internal hardware does not meet the minimum technical requirements for new versions of iOS/iPadOS.
Many App Developers have also dropped support for older devices and iOS versions preceding iOS11/12 (some, for technical reasons, also dropping support for all versions prior to iOS/iPadOS13) - and have withdrawn older versions of their Apps from the Apple App Store, now limiting utility and usefulness of older devices. If you reset your iPad at any time, you may irretrievably lose existing App downloads.
If Apps that you need to use now have higher minimum iOS-version requirements, your only option is to replace your iPad with newer model. Even the basic current iPad model supports current iPadOS 13.x - and has hardware specifications that will vastly outperform your old iPad
I hope this information is helpful.