I want to add music to my Ipod without deleting any of my old music.

I have an old Ipod nano (7th gen) that I use. I havent added any new music to it in over a decade. All the music on it is from the cd's I used to own, not a single thing was downloaded from the ITunes store. The problem is, i dont remember what account I had registered with the device. Now, I have a new account on iTunes bc I want to buy some music to add my collection. Is it possible to do this without deleting all the music already on my ipod?

Those cds became way too scratched to play a long time ago and got thrown away. It would be entirely too expensive to replace my entire collection.