The SAS header onboard is SFF-8643, which is newer than SFF-8087. Out of curiosity, how did you land on an x10 board? Due to cost, we don’t yet recommend it, and it isn’t mentioned in any of our guides. Unless you got a very comparable deal, I would return it in favor of an x9 board or similar and v1 or v2 CPUs to save some money. Performance won’t be noticeably better for the extra cost. Check the Snafu guide for examples on recommended 2011 boards and CPUs.
That aside, you’ll need two (2) SFF-8643 to SFF-8087 adapter cables to connect your backplane to the x10 board you have now. You’ll also need to flash the correct IT mode firmware to the LSI3008 SAS controller onboard.