Hi Charles,
You do not need to upgrade. Your personal license is equal to what is now Enterprise license.
Do you think we can be so cruel as to convert your paid license to the Free one? Never :)
The only problem can be with the product key format. Please, let me know what letter is at the beginning of your key, after "RUT-" part. If you have an old-format key, we will reissue it for you.