I recently acquired an Auto Graflex 4x5 with a Graflex Film Pack Adapter. I have a couple of the Graflex film holders with the slots along the sides but I'm not sure what type of pack I need to use those. Since the film pack adapter is removable, I'm assuming I can replace it with something that accepts those other film holders but I'm not sure what to look for. Any help would be appreciated. Thanks!

If you have 4x5 Graflex 2 sided film holder or a bag magazine they should fit direct into the Graflex back on the Auto without any adapter.

Post a picture of your back by linking to an image hosting site that has the photos.

Here's a link to a few photos:

http://www.flickr.com/photos/56732516@N00/

The film holder definitely does not fit in the current back. Please let me know what you think. Thanks!

No, that film holder will not fit into the film pack adapter.
See that flat bar with the diagonal slots and tab on the right just above the film pack adapter? Slide it to the right, lift the film pack adapter off the bottom fixed bar, sit the 2 sided film holder on the bottom bar with the darkslides to the right, hold the film holder flat against the camera back and slide the top bar to the left until it is tight against the film holder.

The back is the physical part of the camera at the rear of the camera, the film pack adapter, 2 sided film holder, bag magazine, graphmatic are accessories that hold film and attach to the camera back. The accessories are sometimes called "backs" but they are not.

Read the Graflex SLR user manual linked at the heading to this help section as it covers all Graflex SLR's from introduction to end of production either directly or indirectly.