Can I connect my 27inch mid 2010 iMac with mini display port only to the new 27inch thunderbolt display.

I recently purchased a thunderbolt display which Apple advised me I would be able to connect to my existing iMac. However having tried both thunderbolt cables and wirefire 800 cables both suggested by Apple it did not appear to work. I was unsure about the advice I was being given, so decided to return the products, a shame really as I was looking forward to using the new display.

I wondered if the advice I was been given was correct, hence the question to the community.

My iMac is mid 2010 and only has a mini display port, ethernet port and wirefire 800 port plus the usual usb ports etc. whereas the thunderbolt display only has the thunderbolt port and wirefire 800 port.

Any input would be greatly appreciated.