You were probably sold the card without what is called a "dongle". Funny name I know, but that's what it's called. This is an adapter cable that plugs into the card then into a regular CAT5 cable.
Without this cable you're screwed. You'll need to order another one from 3COM.
FYI. The new 3COM's have a popout XJACK. this eliminates the need for a dongle. The cable plugs straight into the jack.
Good luck, I hope you got a good deal on the card, because the dongle might cost you.