Your engine likely has the 6 plastic carbs, and 2 three barrel throttle bodies. If so, the main jet (High Speed orifice) is behind the brass plug in the base of each carb. The idle jets are in the throttle bodies, but are adjusted by a needle valve, thru the carb bodies. The carbs should have a side plate.
There is an intermediate air bleed orifice in the carb body that can get clogged as well.
If you think you need a carb rebuild, you will need 6 kits, and to remove and disassemble the carbs. It makes sense to replace the inlet needle and seat, and the floats as well.
Get a workspace set up with the kits and tools, and remove and clean 1 carb at a time. A spray carb cleaner is good, but wear safety glasses to keep it out of your eyes. When it is off the motor, see if you can clean the idle passages. On my '98 150HP Johnny, that are easy to get at, once the carbs are off. Removing the idle needle will require you to adjust all carbs upon reassembly. That can take some doing. I have had luck removing the side plates on the throttle bodies and spraying the inlet needle and passages from there.
A Carb rebuild will not help your issue, if she runs good when warmed up. If she just stalls when cold, you likely have another issue (choke primer, Quickstart system).