If you're using iCloud Photos sync, you didn't "moved" your photos/videos, you just synced them to iCloud, but they are still on your iPad too (so that if you delete one picture from your device, it will be deleted from iCloud too).
That said, if you need to make room on your device, you can take a look at the section "Store your photos and videos in iCloud" in this support article:--> Manage your photo and video storage - Apple Support, and optimize your storage
or, even better, take into consideration to copy/archive your photos/videos on a computer (using this procedure:--> Archive or make copies of the information you store in iCloud - Apple Support
When your media or other stuff are safely stored on your computer, you can delete some of them from your iPad (or from iCloud) to make more room.
Regards
Giulio