@Howard-Rosenstein You can use the same one. You can activate the current version of Music Maker on two computers as far as I know. Technically, you can install it on more than two computers, but it can only be unlocked on two computers at once. If you want to use it on a third computer you can deactivate it on one of the first two computers.
Be aware, an upgrade is simply a full version for a reduced price. You don't need to install a previous version. Simply download the current trial version of Music Maker or download the installer from your customer account at Magix.com and enter your customer account e-mail and the serial number after you have installed and opened the software.