that USB adapter looks pretty nifty, although from the look of things you would also need a USB cable right? if you're not going through USB then all you need a simple adapter going from 1/4 inch to 1/8 inch. they're usually about $2-3 at electronic stores (usually with headphone accessories)
you can tell if the adapter is stereo or mono by the amount of stripes on the metal pole (like in the pic - 2 stripes = stereo).
if you're running a mono cable then a stereo adapter won't make any difference. just double your track and call one 'left' and the other 'right'.