The Nano should work with iTunes latest version that Panther supports (it's the player, not the OS that you should be thinking about). Under the Apple menu, select Software Update, or in iTunes, select iTunes>Check for Updates...
Not sure exactly what you intend to do, but the individual files' path (assuming you haven't done something weird with them) is:
(Computer)/Users/(You)/Music/iTunes/iTunes Music/(Artist)/(Album)/(Songs)
The stuff in parentheses is unique to you & what you're looking for. Remember that you have to have the files in a format tht in playab; by whatever player you want to use.