You gotta scroll down in giver orders. The option is hidden under there.

if there are a "take corpses" and "get corpses" zones npc will do it from time to time on their own. or you can order them from any place.

if there are no designated zones they;ll start piling corpses around your location to a spot where you were standing at the time of giving the order

to give order you need to come close to npc (or call him to you) and select "survivor NAME" menu. there will be "give order" you're looking for,

I see! Thank you all