i lost my rank on prison(c) when i got elite i have no proof of me having c but i can still enter it altho it says im in d.
You are still able to access the "C" mines, just your [C-prisoner] prefix has changed to [D-prisoner] correct? If so I will request a prefix correction for you.
If you used to be any rank on Prison, then you donate and lose your rank, you are still that rank technically. You can still upgrade to the next rank when you get enough money.