From my knowledge the only plans Hitler had were for sending people to British Palestine under the Haavara agreement. The camps built before the war broke out were to hold people until they could be sent away. This changed when WWII fully broke out, they were then used to hold people in a similar way that Japanese Americans were held in internment camps, mostly as prisons and holding facilities, just that they would also be put to labour for the sake of the war effort. There was little they could do with the camps because they were underway fighting a two front war, so when the Americans and British started bombing supply lines this caused typhus to spread rapidly. Zyklon B is a pellet based insecticide used to prevent typhus which spreads through lice, and people would be stripped of their clothes to disinfect them. The same amount was sent to supposed "concentration camps" and "death camps" according to invoices.