2002 Volkswagen Jetta radio dosn't work

You stated "my battery went dead and now the battery won't work. Is there a code to use to get it working again?" There is no code to bring your battery back to life except to pray and hope Jesus will revive it.
But I think you're talking about your radio? There should be a code to bring it back to life, if you do not have one you will have to remove it and there's a tag on it with the number that the dealer can give you the code.