You must disable the Activation Lock before you'll be able to reuse the iPad with a different AppleID - and you should do so while the email address that identifies the associated AppleID account remains accessible/active - as otherwise it may be become very difficult (if not impossible) to release an Activation Lock from an iPad or iPhone.
If the AppleID Account itself has actually been closed before devices associated with the account have had their Activation Lock removed, it's effectively "game over" for those devices.
Here are Apple's directions for the necessary steps to prepare an iPad for a new User or disposal:
What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be satisfied:
Activation Lock for iPhone, iPad, and iPod touch - Apple Support
Turn off Activation Lock – Apple Support
As you will discover, unless you are the owner of the AppleID that was last used to activate the device, you’ll not be able to defeat or bypass the Activation Lock. With documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple may be prepared to assist - otherwise they and nobody here will be able to help you.
If you have the necessary documentation, Apple have introduced a portal though which you may be able to request release of an Activation Lock:
How to remove Activation Lock - Apple Support & start an Activation Lock support request.
AppleID
You may also need your AppleID and associated password. If these have also been forgotten, they can be recovered here:
https://iforgot.apple.com
To recover your credentials, you’ll need access to one of the following:
- Your primary email address mailbox that corresponds with your AppleID
- Any of the secondary/recovery email addresses that should be configured for your AppleID account
- Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID
More information about recovery of your AppleID and associated Password:
If you forgot your Apple ID - Apple Support
If you forgot your Apple ID password - Apple Support