You got it now.
Order the tank, and then the single coil carts separately. And don't forget about a drip tip for a mouthpiece, if you don't already have some.
As I said before, you can put a single coil cartomizer into a dual coil (DCT) tank. The most important thing to check is that the tank and the carto are the same length.
Standard tanks require a 35mm length carto. These are the standard length Boge or Ikenvape cartomizers.
DCT or XL tanks require a 45mm length carto. These are the Boge XL, Ikenvape mega, Smoktech replacement cartos.
All of these can be found somewhere with pre-punched holes for use in a tank. Or, a carto punch tool can be purchased to punch your own holes. Pre-punched holes can be either laser-drilled, or tool-punched.
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carto punch tool and tool-punched and laser-drilled cartos, both considered "pre-punched"
I happen to prefer the laser-drilled carts. Despite the fact that the holes are smaller, they wick as well as the tool-punched in my experience. In addition, the tool-punched carts always seem to have a slight deformity after being punched by the tool. They are slightly oval, not round. It can be difficult to put that oval shaped tube into a perfectly round endcap. That can cause stress on the rubber o-rings in the endcap which prevent liquid from leaking from the tank.