by Gerald Grow.
Ken, thanks for your generous response.
I have discovered that what we created was not a Moodle "course" but a Moodle "front page," populated with HTML files created as Activities that are accessed through the dropdown menus created under Theme Settings.
We were trying to make something that works like a WordPress page, but has the look of our other Moodle pages.
As far as I can tell, a backed-up Moodle front page cannot be restored by itself, but must be restored into a Moodle course. A blank course seems to work, but I now need to fix the internal links.
My original problem has morphed into a different problem, which I'll be working on.
If anyone has looked at restoring a front page and found something useful, please let me know.
Thanks.