I am not a pro editor. I have Avid Composer Ultimate and have two cards on Atomos recorded on Avid DNX format. They are HUGE! while they open into the timeline, how do I convert the finished file or can I convert these two files into another usable format? This is not client based, daughters wedding 3 years ago, still can't figure out how to make this happen...another anniversary about to happen and Dad still doesnt have a finished video! HELP!

You have two finished videos that you want to make into files you can share, or you have two long recordings that you want to cut up and make a video out of?

I have two hour plus recordings. The file size is workable in avid to edit...I mean I can watch the video and cut and edit dissolves. In my little understanding of all this, after I get a finished product, in order to watch the master, the cards need to be mounted...how do I export or convert what is in the time line? 

In order to tell you the next steps in the process, it would help to know how you got to where you are now. How did you get the footage from the cards into Media Composer? Did you link to the footage, did you link to the footage and then transcode it to another resolution, or did you import the footage?

it sounds to me like you have a timeline built, and need to go to the "File"  "Export" tab and create your master output.

Pick an existing preset, or create your own.  (Quicktime movie or mp4)  (ProRes or DNXHR or H.264) 

Set your audio to stereo output.

Save it to a local drive, and you can unplug your camera cards.

Well the workflow is different if the footage was linked or linked and transcoded. Please answer Carl's questions.