How to recover iMovie supporting files after failed iPad2 transfer! Lost son's project!

Today I transferred (using iTunes) a batch of media files from an old iPad 2 to a MacBook Air. The iPad is running 8.2 and the MacBook is running Yosemite 10.10.5.

The problem is that I ticked the "delete files after transfer" box, so the files are no longer on the iPad. The files are all now imported to the Mac, but the movie project my son completed is only on the iMovie app on the iPad, but without supporting video and still files.

How to solve? Move the files back to the iPad and the extport the movie?

The objective is to eliminate the iPad altogether. It's old and no one uses it. But now I've got the data in two places. The "movie" but with no supporting files is on the iPad; the files that make up the movie are on the mac. But the mac doesn't know it's a movie, so I can't open it in iMovie on the mac. It's just a bunch of files.

Any ideas?