Transfering all photos from old iPad
If you can get access to a Mac or a PC, you should try the iMazing application.

It allows you to selectively copy data from your iPad. You should be able to get all photos from the Photos app. I believe iMazing can also copy individual apps and their data from one device to another.

The iMazing application can also create backups and lets you browse those backups. Make a backup. Save it to a USB pen drive. Whatever method you use to transfer photos from your old iPad to the new iPad, that USB stick will be your safety net. Keep it around until you are sure the new iPad has all the photos.