Thank you all for your input.
After further investigation of 4 wires on the cord, going into the control box the black wire was a dead end, so that left me with 2 hots and a ground, after I connected the plug, off she went, great machine powerful and will sew anything I put under the foot including firm leather. Thread trimmer, thread wiper, auto back tack, programmable etc etc.
I was worried it was 3 phase even though it said single phase on the control box! It had a 3 phase sticker above the box?
The NEMA 6-20P plug worked well.