You should probably stop calling them “AUP files.” The AUP file is a project manager text file. You’re trying to manage Audacity Projects and those have unique rules.
There’s always “a way”, but not always “an easy way”.
There’s no “easy way” that I know of to export audio from multiple Audacity Projects as a batch process.
One way that is possible, would be to use an automation app such as AutoHotKey (https://www.autohotkey.com/)