ipad stuck on verifying update

Something has stalled during the process. Begin with a forced-restart of your iPad - and repeat the update attempt.

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

If the problem with verifying and successfully installing the update persists, you may need to delete the failing/failed update package from the iPad...

Settings > General > iPad Storage

Scroll down the list of Applications until you find the Apple Update - then tap and select Delete Update.

Next, force-restart your iPad as described above.

After restarting the iPad, attempt to update the iPad:

Settings > General > Software Update

I hope this proves to be helpful in resolving the problem.