Q: I had a ipad stolen, I bought a new ipad. I'm setting up my new Ipad at this time. How can I tell which Ipad this email is talking about being used?

What email are you referring to your post's title, where are you seeing it ?

If your old iPad goes online and it's still linked to your account and 'find my iPad' is still enabled on it then it might be able to locate it.

Where are you trying to download your music from e.g. via the Purchased tab in the iTunes store app on the iPad, or syncing it from your computer's iTunes ? Whether you can redownload music from the store depends upon what country that you are in, and whether it's still in your country's store. If you can't redownload music then you will need to sync it from your copy of your library on your computer's iTunes - or is that what is not working ?