Connecting Macbook Pro to iMac

Thank You for your help!!

I'm using a 20 inch iMac from early 2009 (iMac9,1) with the operating system OS X El Capitan. I want to connect it to my 13 inch Macbook Pro from early 2015 (MacBookPro12,1) using a Mini DisplayPort Cable.

I'm having issues connecting the two, I've tried every possible combination of Command-F2 and Command-Fn-F2 when both computers are logged in to the MacOS user account as well as when one of them isn't logged in.

I think that maybe my iMac isn't on the compatible iMacs list and I'm hoping that you could help me! Is there any other way for me to connect these Models? Another suggestion could be maybe an adapter from Mini DisplayPort to Thunderbolt 2 but after that I'm all out of ideas.

Thank you in advance!