What "upgrade" did you install into the admin system? And more to the point, what PROCEDURE did this "upgrade" involve?

Who are the providers of this "upgrade".

"Upgrade" and "Admin" are not terms that usually go together in zencart...

The error is being caused by a piece of script (php) that looks for data in a table called zen_admin_files. ... and this table does not exist, it seems.

Generally speaking, you can have additional tables in the database that can lie "dormant", as a database is little more than a repository for information.

So... GO THROUGH the original module (you must have a copy of it on your hard drive) to see what php FILES are used.

REMOVE them from your admin directories, and if any of the CORE files were replaced by the "upgrade", then these need to be restored to their original position.

DON'T mess about in the database... The problem can be resolved in the ADMIN FILES.

It would be good to know HOW you did this install...

Did you run any SQL patch during the install?