Cannot delete synced media from iPad

Then you'll need to sync to a different Mac or PC and as said sync empty albums for songs and photos and sync an empty folder for videos to remove whatever was synced.

The other option is to reset your iPad and set it up again from a backup. Backups don't include synced content.

Sync media refers to things transferred or synced form a computer.

The usual way to remove that is to sync again from the computer and remove them or sync an empty album or folder instead of whatever was synced.

You need to figure out what was synced from a computer and then unsync it.

It should list the apps the contain the synced media below that. Like Music, TV, Books etc..

In the apps below, you should be able to then delete specific media by swiping the item to the left.

click here ➜ Sync content and remove synced content between your Mac and iPhone, iPad, or iPod touch - Apple Support

What is under the portion of the screen you show above? Surely you will see things there like “Music” with additional details.