do I need to buy in order to change my pension to orops can some one explain what we have to do in order to get medical in Cyprus ie by or rent

As long as you are in receipt of state retirement pension you will be entitled to use the state healthcare system here.
You need to get a form S1 from the DWP and take that to the citizen centre where you will be given a hospital card.
It doesn't matter whether you are renting or you buy.