Question about buying a pistol from a private person in Iowa

[FMarlon]

If I buy or trade a pistol from a friend of a friend, how do I do it legally? Do I need to go to a ffl to transfer it to my name, and what if it hasnt been legally transfered for the last couple owners? To my knowledge, this pistol is not stolen and the last 2 people I know to have owned it are both legally able to buy and own handguns in my state.(Iowa)

Help me please.