I don't know what do you mean with "GSX 3.6.1 was a mess", it surely worked fine and, whatever your problem was, it didn't require a complete reinstallation, let alone a deactivation of the license.
But even if you did the unnecessary deactivation, there's nothing to copy or no file to handle. If your license is not active, when you click Install, you'll be asked for your Activation key, which is the code in your purchase receipt that starts with an A. There's nothing else required.
If you lost your key, click the "Get your keys" button in the installer.