Are there any SATA to USB3 connectors?

I have a Dell (not recommended) Studio XPS Desktop 7100 with one PCIe slot which is populated with my NIC. I do have one open PCI slot and a total of 6 SATA connectors (one is free). I have seen, at the local Fry's, USB3 to SATA boards. Is there such a thing as a SATA to USB3 board or connector. I have seen, on Google, several companies offering PCI USB3 boards, but when I go to the website all they have are PCIe and PCI Express boards. I really can't afford a new motherboard. Then I would want to go to an 8 core AMD Phenom which would put me further into the poor house.