Put the iPad into Recovery Mode
Connect the iPad to a Mac or Windows PC with a USB cable
Open Finder on Mac or iTunes on Windows or older macOS
Select the iPad when it appears
Choose Restore
Wait for the restore process to complete
Set up the iPad as new or restore from a backup
If Activation Lock appears, enter the Apple ID and password previously used on the iPad
If you do not know the Apple ID or password, contact Apple Support with proof of purchase