Does the iPod currently turn ON and work as an iPod (when not connected to computer)?
iTunes on a Mac should recognized an iPod that is formatted for Windows. When you connect it, watch the iPod's screen. Does it say "Do not disconnect" or "Connected" or some other indication that there is a connection? Does it only show the battery charging indicator? Or does it not react at all to being connected?
The first step is getting the iPod recognized on the Mac. After that, you can off-load songs from it, IF you don't have access to the iTunes library directly from the old Windows PC (which is a much better way to transfer your complete iTunes library data to the Mac), or if you don't have a backup. An iPod is not designed to be your iTunes data backup. So, if you still have your old Windows PC with its iTunes library intact, use it instead of your iPod to get your iTunes library on your Mac. Please post back with the details.