My iPod classic no longer syncs with my Mac
Are you saying the iPod DOES appear in iTunes, but does not sync? Or are you saying it does does not appear in iTunes, so you can't sync it?
For some reason it even says windows format.
An iPod that is formatted for Windows works fine with a Mac, because Macs can read and write the Windows format used by iPods (FAT32). Some models are formatted for Windows by default, even when used with a Mac. My old 3rd gen iPod is formatted for Windows, and I use it with my Mac. So that's not an indication of a problem.
It doesn't even show up on devices in preferences.
Only iOS devices appear there; the only iPod that would appear there is iPod touch, not iPod classic. So that's not an indication of a problem.
If the problem is the iPod not appearing in iTunes, do a Reset (restart) of the iPod. A Reset does not affect data.
Learn how to reset your iPod - Apple Support
Disconnect all other USB devices from the Mac. You can leave standard USB keyboard/mouse connected, if used. If you have not recently, you may also want to restart the Mac. Run iTunes and connect the iPod to a direct USB port on the Mac.
If it still does not appear in iTunes, watch the iPod's screen when you connect it. Does it say "Do not disconnect" or "Connected" or give some other indication of being connected? Or does it only show the battery charging symbol? Or does it not react at all to being connected?