You would get something like this:
http://accessories.musiciansfriend.c...ter?sku=339511
...and then 2 intrument cables to go from it to the Mbox.
Your keyboard is a consumer keyboard (no offense). More pro keyboards would have individual line outs for hooking up to an interface, mixer or PA.
The one you have uses the headphone out, and you can jerry rig it this way.
Page 9 of your keyboard manual.