iMovie

iMovie should have come preloaded on your Mac when you bought it new. If you perhaps bought a used computer pre-owned by someone who had wiped iMovie from the drive, the previous owner would have a different Apple I.D. than yours. Then you probably cannot get iMovie, at least not through normal channels. There are some non-Apple approved websites out there that purport to provide a downloadable iMovie 10 app.

You might take a look at this link and see if anything in there helps you -- particularly the post by spectre_gholst.

iMovie for High Sierra 10.13.6 ???? - Apple Community

-- Rich

There should be an iMovie 10 icon amongst your purchases. provided that you had iMovie 10 on your Mac before, even if you had deleted it. If you don’t see it, click on the Get Information item, or maybe it’s More Information, at the top of the Accounts window screen. Another sreen will then open where you will have the option to unhide any apps that may be hidden.

— Rich

Sign in to the app store and view your purchases from your Account purchases list. Download iMovie from there.

• Rich