Dispel magic says:
If you target an object or creature that is the effect of an ongoing spell (such as a monster summoned by summon monster), you make a dispel check to end the spell that conjured the object or creature.
If a summoner uses summon monster 3 to summon multiple lower level creatures (lets say 3 earth elementals) then am I correct in reading this as saying that a dispel magic targeting any of those three elementals will dispel all of them?
They were all summoned by the same spell so even though there are three elementals dispelling one will dispel all three.