Can you explain what you want to do ?

I have two polaroid one 636 and one 600 and wanted to change the film's 636 has 2 photos to the 600 to see if it has more quality.

you can make it.
you only need a black sheet.

In a dark place, you can take of the cartridge from the first camera.
Then, put the black sheet on the cartridge. You can exerce yourself before with an empty cartridge.
The black sheet must be over the photos unexposed. When the sheet is in place, you can turn on the light. 
Then put ths cartridge in your second camera.

I perform film swaps in both my integral and 100-series cameras all the time. I've been practicing since I was a kid back in the 80's, so I have it down to a science.  All of the integral cameras (to my knowledge) will eject the first photo before you take a picture unless you re-install the cardboard darkslide that comes with the pack. I change mine out in both the integral and 100-series cameras in a roomy closet I have- that way I can actually have a little room to work and do what I need to do without rushing. Peel-apart films are far easier- just switch them out in a dark place and be sure to put the small pull-tab back in the right place before closing the camera back. The only cameras I've never successfully (not that I tried too many times) swapped-out were my roll film behemoths. I'd be happy enough to have any film for those now, so "swapping" isn't even a thought...

You can switch integral film packs. Rever to this tutorial, and the video

http://support.the-impossible-project.com/entries/237836-change-cartridges-in-your-camera-without-losing-a-shot
http://vimeo.com/16630738

Good luck,
TRB