If you ever had iMovie 10 on your computer but perhaps deleted it you can sign into the app store, click on your name at the bottom of the app store to open your purchases folder where you will see iMovie 10 listed, and then you can update it from there onto your computer. iMovie will update to the highest version compatible with your computer's High Sierra OS. That would be iMovie 10.1.8 I believe.
Best iMovie Alternative to Fix All iMovie Probelms - Recommended. Filmora Video Editor is the best alternative to iMovie for Mac (macOS 10.13 High Sierra included) I'd like to recommend to you. It's easy to use, even for beginners in editing videos can start the editing right away. IMovie 10.2.3 - Edit personal videos and share them. Download the latest versions of the best Mac apps at safe and trusted MacUpdate.
If you still have an older version of iMovie 10 on your Mac, then you would first need to drag it from the applications folder to the trash, but don't empty the trash, and then sign into the app store to update it from the purchases folder per the above. If by chance unsuccessful you can drag your present iMovie app out of the trash and return it to the Applications folder.
Imovie 10.13
-- Rich
Imovie 10.13.6
Mar 17, 2020 11:42 PM