It would take alot of firepower to completely destroy a terminator single shot weapons I would go with a Barret 50 cal and a 40mm grenade launcher with HE (Heavy Explosive) rounds, keep my distance I wouldn't want to get to close.
Now a GE Mini Gun would do nicely for taking down multiple Terminators it would have to be mounted on a humvee or a helicopter 3000 rounds a minute with Armour peircing rounds (depleted uranium) tipped shells would go right through them believe me it go through tank armour it would take out Terminators wholesale.
now If I had air support I would call in A-10 warthogs 30mm Gau-8 a modern gatling gun similar to GE mini gun but on a much larger scale , the whole plane is basically a flying gun its built to widthstand several direct hits has armour completely around the pilot like a tank.