Never heard of a Stepcraft before but a little research showed that it was a Kick Start project a while back. One of those multiple process machines (mill, 3D print, etc.).
According to this video: https://www.youtube.com/watch?v=mOsSU2hGvik
you save as Mach 2/3 (mm) (*.txt) files.
I suggest you look at your manual or call the manufacturer support line. Otherwise you can search the internet a bit more like I did. You seem to be close to making it work! You just need to figure out what kind of post processor to use...