Problems transferring iMovie events/projects to new iMac

I have quite a few iMovie projects (with the associated events) on my 2008 iMac (which I still have). Obviously, I spent hundreds of hours creating these projects, complete with added soundtracks, title slides, transitions, etc. I was able to copy all the files to my 2021 iMac with the M1 chip, but virtually all of the iMovie projects are messed up.

For instance, I have one project where the slides are all in tact, but the soundtrack (imported from my Music file of over 20K songs) is missing (even though it appears in the timeline). When I pulled up the Audio Library, it showed only a couple hundred songs in it, not the 20,620 I have in my Music library. The song for that soundtrack was not one of those shown.

On another project, the video and title slides are all there, but they are not integrated as they were when I created the project. There are several slides that are labeled as Missing File, including the soundtrack (similar to described above).

In summary, it is a total mess!

When I look at the contents of the iMovie Library, there are 82 folders and files, but only 34 show up as events in iMovie. The files include CurrentVersion.flexolibrary, CurrentVersion.plist, and settings.plist. There are a couple of folders that didn't make sense to me either; Updated Projects, and _Temp.

In addition, I wanted to categorize my iMovie projects by creating a number of iMovie libraries, such as Family, Vacations, etc. When I use iMovie to move a project from the iMovie Library to one of my new libraries, it loses its name, which is replaced by a folder with the date the project was moved.

How do I get this all straightened out without recreating all those iMovie projects I constructed over the last 16 years?