If you are running an older operating system (like High Sierra 10.13), the App Store may allow you to download the "last compatible version" if you have previously "purchased" or associated these apps with your Apple ID.
While these apps were originally free for users who purchased new Macs after October 1, 2013, existing users on older systems like Mountain Lion (10.8) often sought the last compatible versions (such as iMovie 9.0.9 or GarageBand 6.0.5) before the "iLife '13" transition. ilife 13 download full dmg hot
iLife '13 was specifically designed to run on and later. If you are running an older operating system
Modern versions of iMovie and GarageBand are available as free, standalone downloads on the Mac App Store for current macOS users. Modern versions of iMovie and GarageBand are available
Requires an Intel-based Mac with at least 1GB of RAM (though 4GB+ is recommended for video editing) and several gigabytes of disk space. How to Download iLife Apps Today