If Find My iPad is enabled, you cannot fully erase and reactivate the iPad without the Apple ID password
Put the iPad into Recovery Mode
Connect the iPad to a Mac or PC with a USB cable
Open Finder on Mac or iTunes on Windows or older macOS
Force restart the iPad and keep holding until the recovery screen appears
When prompted, choose Restore
Wait for the restore process to finish
Set up the iPad as new after it restarts
If Activation Lock appears, enter the Apple ID and password previously used on the iPad
If you do not know the Apple ID password, contact Apple Support with proof of purchase
If you only want to erase the device and know the passcode, go to Settings, General, Transfer or Reset iPad, Erase All Content and Settings