Frank, that is certainly what other people have reported having success with. There are a number of ways you can find out your Windows 10 product key, findable by a Google search.
It would seem, from looking at this thread, that a lot of people have had problems. I upgraded my old Dell PC to the beta preview a few months ago with no problems. Then on the 29th July I upgraded my current PC to the public release, also with no problems. Then a day or so later, I upgraded my Asus T100 convertible, again with no problems, even though it only has 32GB of storage space. In each case, the machine boots faster, runs faster, and feels more solid. And, so far, all my programs and apps run fine. In my opinion, it's well worth upgrading provided that you know how to restore if things go wrong. But I also understand if people want to wait a while. Being an Early Adopter is a little unsafe...