Unable to Purchase Products in Marketplace

I think I will kill 2 birds/ 1 stone etc.
I have been planning to go from Monthly Game Pass Standard MSFS version to the purchased Premier Deluxe version.
Can I get the latter other than via Marketplace, & what do I have to watch out for as regards licenses if I delete the Standard Version?
I would cut & paste existing Community folder to another holding drive to be put back on to Premier Deluxe , when it is installed.
TG