If you are the legitimate owner then you can reset your Apple ID password in a browser online (maybe at iforgot.appleid.com from memory). You’ll need access to the email account and/or two factor to do so to prove your identify. Then you can log in online to remove the device from your account.
There are a few legitimate reasons why you may be the owner of an iPad that you are locked out of and this should work if you are. Apple has a great set up and it’s designed to protect theft.
The other way around it is to produce your receipt for the device and take it with the device to an Apple store.