How old do you have to be to pickup a firearm ordered off line?

Will need background check. Then have to give copy to your city Police department

You must be 18 to purchase a long gun and 21 to purchase a hand gun.

Depends on the firearm ,first of all you had to be old enough to order it . I guess if you were old enough to order it you should be able to pick it up you have to fill out ffl paper work and fill it with the state of MI.