How do I get a mmeory card out of the DVD slot?

very very carefully turn the iMac to the right so the optical drive and SD slot are facing down... try to shake it out like a bully shaking my lunch money???

or....not recommended -- unplug the unit and press and hold the power button to discharge the capacitors and use tweezers and a super bright flashlight and possibly fish it out and hope to not do damage to the optical drive....

or ..... take to genius bar and have them remove optical drive and remove the SD card... might cost you a few bucks because it wasn't apples fault... but genius bar has always been super helpful for me and never charged me even out of warranty. although my experience may not be what you receive.. different stores different employees and i'm a haggling pro.

Or..........Upgrade to Mac Pro where you can open the computer up in 5 seconds.😉

Make an appointment with the genius bar at your local Apple retail store. You don't want to damage your mac trying to extract it yourself.