How to import iMovie HD 6 and earlier iMovies into iMovie 10
I have several old iMovie files created in iMovie 6 HD and earlier versions of iMovie that I would like to import into iMovie 10 (Mojave). These older files are stored in folders by subject content (not within the Movies folder). I can't manually import the files and iMovie 10 will not see the files and upgrade them to be used in iMovie 10. I also can't import the .mov (Quicktime) files that were created long ago from the iMovie files. Can anyone provide instructions on how to get my old iMovie files into the new version of iMovie?
iMac (Retina 4K, 21.5-inch, 2017), macOS Mojave (10.14)