By moving their current (non-working) iMovie to the trash and then going to their
If your current macOS is older than the latest iMovie requirement (currently macOS 15.6+), a prompt will appear asking if you want to download the last compatible version for your system. Apple Support Community How to Verify a DMG File If you have already acquired an iMovie_10.3.3.dmg imovie 1033 dmg verified