Plug your serial number in here;

http://www.chipmunk.nl/klantenservice/applemodel.html

If the machine did not come with an airport card you can't just put one in. It was a factory or Apple Tech installation only, it required more than just the card.

If you need wireless this should work. It should be plug and play, no driver needed. It does come with a driver CD though if you need one.

http://www.ebay.com/itm/180556350408