No firewire-USB adapter will work. A compatible firewire card is pretty easy, just get one that fits an open slot in your machine, AND make sure it uses a T.I. chipset(though this is not as crucial as it used to be
).
PT11 on Windows 10? Not sure its supported, but it may still work. "Not supported" means it is untested and you may not be able to get help from Avid in case it doesn't work(but it may work anyway).
Be prepared to fuss with things and keep your fingers crossed(but also, be aware that you may end up needing to upgrade both PT and the interface). The good news there is that A-the current version of PT adds several features that you don't have now(like more tracks, VCA's, Folder Tracks...). And B-there are several good interfaces that can replace the Mbox 3 pro(and will sound as good and may cost a lot less). In a real pinch(as a last-ditch experiment), you could try using ASIO4ALL instead of Avid's Mbox driver(this would be a total "hail Mary" and if it didn't work, I would immediately uninstall ASIO4ALL)