The screen on my iMac is shot, nothing but a black screen. From what I've read, air display and screen recycler needs files to be downloaded on both computers. Hard to do when the screen is not functioning on one of them. There's got to be a single cord that would work.
Since you did not mention that in the original post, I could not have guessed that scenario, as I guessed you wanted to extend the iMac's screen with the MBP's display.
This is not YouTube or Twitter, where you are limited to few characters, thus you are able to explain the full problem quite well.
Anyway, a Firewire cable and
Target Disk Mode will let you access the iMac's HDD via your MBP and get the files off from it.
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Edit:
Would it be easier to connect the late 2009 iMac to a 2012 iMac?
Since you can also edit your posts, explain, that the frelling screen is broken and what you actually want to do.
It is either simple and the year of the iMac's release does not play into it at all, as you can connect an iMac from 2002 or 1999 to a Mac from 2011 quite easily via Firewire or Ethernet, depending on your actual needs.