If I read it correctly, you have the AC plugged into a 220 wall recepticle. But check the rating on that receptical to make sure it's 30 amp rated. Just the arrangement,angle, & size of the terminal openings should let you know the amps rating.
Then go to either a good hardware store or elect supply and buy the correct plug end and a short length of the 10ga cord wire that is made to be used as a cord. I know Home Depot & Lowes has plug ends in most types, but I never looked for "cord wire by the foot" at those places.
Yes you can buy a pigtail someplace, but it's easy to make one.