MiniDisplay Port Question

Hello all of you!

I have an (Early) 2009 iMac 24-inch and I also own a (Mid) 2012 MacBook Air 11-Inch.

I would like to know what MiniDisplay Port or Thunderbolt cable I need to connect these two computers together because although I have had apple for most of my life I still don't know very well all the cables and other peirpherals I need to connect both of these computers together.

Please could you link me the product to the official apple.com/uk or if you could also link me it to amazon.co.uk