Help with Grand Theft Auto San Andreas!!!?

Okay, so i go to load game and the mission it says im on is puncture wounds... but when the only mission thing i can find is Zero's airplane mission where i have to kill all of the couriers... and i cant seem to do it!!! im gonna ask my brother to later... and i did the mission at toreno's ranch with the "?" now I DONT KNOW WHAT TO DO!!! Help?!?!!?!?1?!!?!?!!!1 PLEASEEEEEEE... oh and this is for xbox!!:) PLEASE HELP, IM FREAKING DESPERATE.