Hi I'm looking for a thunderbolt extension cable so I can hook up my 27" LED THURDERBOLT APPLE DISPLAY SCREEN.

I don't believe TB extension cables exist at this time.

Extension cables for Thunderbolt don't yet exist, but Apple has recently released a Thunderbolt cable that is 2M or 6.5 feet long. I just connected my 27" Thunderbolt display to my iMac, which sit about 4-feet apart from each other, and it works perfectly. You just don't use the Thunderbolt connection cable that is attached to the display - plug the display's power cable in, and use the 6.5-foot Thunderbolt cable to connect the display to the computer.