If my memory is correct I would say 12awg. 10awg at the most. I can look tonight.

You'll struggle using 6awg. That's pretty stiff even in braided copper.

General rule of thumb.

12 AWG - maximum of 25 Amps in free air, maximum of 20 Amps as part of a 3 conductor cable;
10 AWG - maximum of 40 Amps in free air, maximum of 30 Amps as part of a 3 conductor cable.

6awg you'd be able to run your range or dryer at 60amps