iPod nano transfer music

My brother in law has an iPod nano since 2013 which is nearly full of music ( looks to be a mix of purchased and ripped from CD collection) and the battery needs to regularly charged. He asked for our help as wants to transfer to newer device or PC. I have limited knowledge of iTunes or iPods. Have tried a few things

I can’t backup the IPod to iCloud as says needs iOS 14 ( it has 12.5.7). Not sure if that would help as under Settings ITunes Wi-Fi Sync - unable to resume sync until (old) PC available . We no longer have the PC and if we connect IPod to iTunes on new PC the music on IPod does not sync to PC. We do have a copy of the old PC files etc on an external drive. Not sure what to do? Is it possible to transfer the music playists etc. another way? Eg sync or locate from the external drive of the old PC ? Not sure what I should look for on the external drive and once found what files I transfer or is this even possible? Thank you in advance for your help.