Installed in 2007, N Series P730, (only difference is the size of the hard drives), version 6.4.2.4681.
Why would I want the MP3 files?

That sw ver. dictates that you have a FAT32 'MP3s' media folder. You can just go ahead and copy the media files from the 'MP3s' folder. You are not looking for '.mp3' files. You may see those if the server was originally setup to dual encode. However that folder also contains the uncompressed '.wav' and '.png' cover art files. If there are a bunch of '.mp3' files you can navigate settings > functions > 'remove dual encoded media'. This will leave you with just the '.wav' media in the 'MP3s' folder.
So yeah ..... the folder has a stupid name.

I thought they had a third party that would extract the files, but I may be thinking of the place that used to load the CDs in bulk for a fee.

Many years ago that was an optional upgrade service if you were updating to newer ReQuest hardware.
In this decade ....... to copy your media in Windows 10 go to Start > File Explorer > Network > then navigate the ReQuest server name and use the drop down folder list > MP3s folder. Copy / paste what you need to USB or NAS drive.

Always had solid email tech support with ReQuest. Never call anyone if I can avoid it :). It's harder to write crap than talk it.
According to their support pages they no longer officially support anything older than the current gen F1/F3 hardware and its siblings.  I think this policy was part of their restructuring deal with the current Swiss owner. Hope this helps.