What you are calling Jack cords are probably what catalogs refer to as 1/4" connectors.
What you are calling "stereo" plugs are more universally known as TRS or Tip Ring Sleeve connectors.
The XLR connectors you are referring to are more accurately described as 3 pin XLR. There are XLR for many numbers of pins.
You can purchase 3 pin XLR to 1/4" TRS cables at any place that does pro audio.
You can make your own too.
This page has all the info you need to solder them correctly:
http://www.rane.com/note110.html best regards,
mike