iPad restore errors are listed here:
iOS update and restore errors - Apple Support
If your iPad is not recognised when connected to your Windows PC (with iTunes for Windows installed) or a Mac computer (with iTunes or Finder - as appropriate for the installed version of macOS), try using a different USB port. Otherwise, this support page may help with troubleshooting connection issues:
If your computer doesn't recognize your iPhone or iPad - Apple Support
Should you continue to encounter difficulties, the technicians at the Genius Bar of your local Apple Store or Apple Authorised Service Provider (AASP) - will be able to assist:
Genius Bar Reservation and Apple Support Options - Apple