i know you have to buy them, but will they just be a folder?

i know you have to buy them, but will they just be a folder?

If you are talking about the actual weapon file:
There shouldn't be any reason to use this since I won't really do anything in bo3, weapon files are just used to store data like damage and recoil etc. The actual weapon is split into models, anims and textures.

If you are talking about models and anims to port the weapon to bo3:
Depends which game.
 - You can use Wraith to extract them from the game while its running(Only works on Advanced Warfare, Ghosts, Black Ops 1, Black Ops 2 and Black Ops 3)
- As for WaW and Cod 4, you can just use Tom's XModel Extractor and XAnim Extractor to get the files needed for porting.

Once you actually get the files you would need to port them to bo3 which is sometimes a long process, I used this tutorial at one point by Azsry: Link(It also shows how to get models and anims from bo2)