So I know you can Just do if Enum.MemberShipType.Premium then
but what if I wanted to do since theres 3 types of membership
one that goes for 2200 robux each month how would I know that speicificly
If you've looked here then you'd know that you can't tell which version the player bought as a developer.
However, the only difference between all of the membership types is the price of the membership and the stipend of robux you receive, so you can just use the MembershipType
as you mentioned in your question.
if you really NEED to know the amount of robux a player gets when they join Premium, then I'd suggest looking into the Https Service