Responding to your choice of the word "upgrade" - don't expect much improvement from a Hub 3 over a fully working SH2ac. If you've got any peak time slow down, a Hub 3 might improve things a little because it uses more channels, but the wifi is no better in my experience.
If you want a 350 or 500 connection you'll have to have a Hub 3, but I doubt you'd ever see the benefit of the speed increase over 200 in real world use.
"What do I do with the older router do I have to send that one back?"
Usually they take it back for recycling, but as the SH2ac is obsolete there's no value to VM, and they'll pay to recycle it. If the wifi of the SH2ac is working, you might want to keep it and see how you get on with the Hub 3, because a potential use of most old hubs and routers is to configure them as a wireless access point in conjunction with the new hub,which could fix any slow or dead spots for wifi. Search on terms like configuring old superhub as wireless access point. It takes about half an hour of following simple instructions to do this. The main issue is that the old hub that you want to use as a wireless access point needs to be connected by an ethernet cable to the new hub, so if you do this you need to think about placement of the access point, and whether you can conveniently and securely route a cable between them.
If the new Hub 3 does everything you want, then just send the hub back to VM (there's usually a reply paid label in posted-out Hub 3 boxes).