Reference without Transform

Hi everyone! Im currently working on a 2D game and have the problem, that I cant reference the bullet prefab. The gun first has to be picked up by a player, then, when the gun is picked up, it gets the "gunScript". (already done!) Therefore I dont think that it is possible to use Transform and drag the prefab into the script. I already did some research and tried a couple of methods, but without success. Would appreciate any help!