Will I lose my save when I switch from Game Pass to Steam?

I bought an Xbox controller that came with a 14-day Game Pass voucher, and then I downloaded forza horizon 4. Now the 14 days will soon be over and that's why I wanted to buy the game entirely on steam. That's why I wanted to ask whether the game / memory status will be retained.

Your question is confusing, but if I get it right then your progress will be lost.

If that was a voucher for 14 days of Game Pass for a platform other than Steam, then you'll have to start over if you want to buy the game on Steam

Probably gone, but you can otherwise buy it in the microsoft store