Bad iMovie data transfer

In April 2015, I bought a brand new MacBook Pro. The Apple Store did a data transfer.

I rarely use iMovie, but when I opened it recently (July), I noticed that pieces of my old projects were missing. Error is "Missing File: MVI_(number) is missing. Try reimporting the original source media." Several Geniuses at The Apple Store worked 2 hours with me and even called corporate tech support. All RAW footage is there, but I would have to re-edit these projects.

Most of these files are from iPhoto. The Geniuses think that when I chose "Photos" as my app, a link was lost. We tried moving the project files from my backup hard drive, but this also didn't work. I am using iMovie 10.0.9 and am current with all software.

I am now burning the projects to DVD from the 2009 white MacBook where these projects were produced. I am wondering if there's a way to move these projects directly from my 2009 MacBook directly into my 2015 Pro. While these are far from being professional projects, they mean much to me.

Thank you!