Jack wrote:
I have to move my stove to the other side of my kitchen for a couple
of weeks due to construcion. It is electric, and from what I can
tell, 220v extension cords don't exist. .

I plan to disconnect the 220v wall plug, wire in a 20 foot jumper
section of #6 cable, then re-attach wall plug to end up jumper. Will
run temporary wire under kitchen floor/on basement ceiling.

My questions is this, are there #6 wire nuts, or so you use a
different technique to connect #6 wire?

You can use #6 wire nuts. The splice must be contained within a
junction box. Make sure that the temporary wiring you use meets code
(i.e. NM mounted correctly, BX, in conduit, etc.)