The pin you're talking about is likely the draw stop, it won't change the draw length, it'll simply stop the draw at a different spot.

Hoyt Fuel cams (and RKT cams) have 3 adjustment methods, swapping entire cams (3 types/sizes), swapping modules (5 sizes), and rotating modules within the cam itself.

You likely won't be able to buy modules yourself, but can keep your old ones when you get the draw length adjusted at a shop. Often, shops will swap modules for free if they keep your modules, but not always. You may be able to find take-off modules online.

You MUST match up the module and position with the draw stop. And you have to verify your timing after you change such that your draw stops make contact at the same time.