You should have an extra large Halon extinguisher and extension applicator on the main deck to carry to the source of the fire and try to extinguish it
Er you are aware that the main deck on the 757 is 14 pallet positions long and there is no access beyond the first one. Unless you have a 30 METER extension applicator and one which could drill through the floor to the belly holds as well then its a non starter.