I did what Brynn suggested, changing my FCP settings to import the stills in at 1 frame in length each, and dropped them into my timeline. Then, I took a bit of Ben’s advice, exporting the 400 frames as a Quicktime file, opening the file in Quicktime, then exporting it again with the settings I desired (Apple Pro Res. and size etc…). The next step for me is to learn how to use motion so I can do some slow pushes and pulls….
There is very likely an easier way to do this that requires less steps, but I took what I understood from above and made it work.
Thanks again everyone!