All that my iPad says is that there was an error installing this update. I don’t know what it wants me to do

If it exists, delete the 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:

• 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.

After restarting the iPad, attempt to update the iPad:

Settings > General > Software Update

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