Managing books on iPad though Apple Devices app

I recently had to revert my iPad to factory conditions and then restore it, due to an error in updating the OS. The update app backed up my iPad to my PC before attempting to update the OS.

Now that I have restored my iPad, most of the books in the Apple Books app are gone. Names of collections are still there, but the collections are empty.

Of course now iTunes does not do anything but podcasts, so I am trying to find Books with the Apple Devices app on my PC. Unfortunately Apple Devices will not even recognize Books as a category when connected to my iPad. It does recognize Books when connected to my iPhone, just not my iPad.

How do I find all of my old books? Lots of user manuals, reports, and other documents in those missing documents.

To make things worse, updating my iPad happened right after I rebuilt my PC and updated to Windows 11. All of my old iPad backups are in a backup of my PC drive. I have no idea how to access those old backups now.

There does not seem to be any real documentation for the Apple Devices app. Searches for help in backup and restore of iPad and iPhone still refer to using iTunes.

Any help will be greatly appreciated!