There is no upgrade form Prime to any version. You can upgrade from Artist, which you mostly get for free when you buy PreSonus hardware. There is a special offer until the end of December:
https://shop.presonus.com/Studio-One-4-Professional-Upgrade-from-Artist-all-versions
This is everything which has to do with Studio One:
https://shop.presonus.com/software/Software-Line--Studio-One/page