iPad mini backup via Finder/iTunes not showing on Mac

I have an old iPad mini, circa iOS 12.5 that I've used mainly for reading Kindle books, and I had the option to "back it up" to my Mac, so I did. So far, there is no indication on the Mac that any such thing had been done. No trace of added files, nothing Backed Up to the Mac. Why has nothing changed?

[Re-Titled by Moderator]

Original Title: "Back up" my iPad Mini?