Hello,
Firstly, we suggest that you never share personal information like your CD key, so we suggest you delete the photos you uploaded once you've read this message.
With regards to your issue, in many cases the CD key you receive when buying a game on steam will automatically be linked to your account if you open Uplay by trying to launch your game from Steam. You can check what games are registered to your Uplay account by clicking the gear icon in the top right corner and then selecting "Account Information". The page that loads will show every product that is registered to the Uplay account you are logged into.
If you do not see Far Cry 3 listed, then please contact the Ubisoft support team and tell them the CD key. They can check what account the key is registered to and help you regain access to your game. You can contact them through our ticket system's webform found by clicking on "My questions" on this page: https://support.ubi.com
Alternatively, if you would like to contact support by phone you can find the contact number for your regional support team here: http://www.ubi.com/US/Support/InternationalSupport.aspx