Hi

In the AWG system, the lower the number, the bigger the wire. The wire on the heated bed is 12 gauge. Extending it with the same thing makes reasonable sense. Nothing else on the printer requires anything close to that fat a piece of wire. 18 AWG would be fine for the rest of it. You will also need a power cord for the gizmo. A used computer cord with one end cut off works fine. For the insulation on the bed, Nomex felt is a good choice.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

There are lots of other ways to go for that.

Bob