how to find where an app stores its files?

I've started using a new note-taking app. It's a fairly obscure app but has some features I really like.

My only issue is that I can't work out where its files are being stored. I can't find them in the Files app, nor in Finder when the iPad is connected to my Mac, nor in iCloud drive.

What I want is to check that the files are being stored locally on the device, and not uploaded to any server. I know that you generally can't access an app's files unless the developer enables it, but is there a way to at least check where they are?