Hokie71,
From what limited number I've seen, the 4 pin square plug is most likely +12v (x2) & Grd (x2). The 6 pin I've not ran across. Have you considered just putting a volt meter on it? Also, not sayin' they don't exist, but I'd be very surprised if you can find a prefabricated breakout board for your Dell supply. Hope this helps.
bd