Graphics card not compatible?

I got a Radeon 3850 for m day, it didnt come with the power cable. There was nothing to hook anything up. THis was a 250 dollar graphics card people, I have a dimension e520 built computer from dell. (http://i27.photobucket.com/albums/c186/darkhen/computer.jpg) Im told the green circle is the SATA power cable, the red circle is the floppy disk chord and the black one is plugged into teh cd drive. I was told to buy 2x molex power splitters, the only problem is the blackcricled thing cant be pulled out. My brother went to pc store and they said nothing would be compatible. This technically means no graphics cards will. By the way, the powerchord should be a 6 prong.