Download of GarageBand and iMovies for Mojave 10.14.16 on MacBook Pro 13"

If your Mac can be updated to the current version of macOS, then you can only download the current version.

The App Store usually offers an older version of apps to legacy Macs that can't be updated and then only if you have previously downloaded the app.

M1 Mac mini, macOS 11.5.1; Watch, series 5 GPS/cellular, watchOS 7.6.1; iPad Pro 2nd Gen, iPadOS 14.7.1; iPad Air 2, iPadOS 14.7.1; iPhone 12 Pro, iOS 14.7.1; TV 4th Gen, tvOS 14.7  HomePods, audioOS 14.7 and Airport Express w/ Airplay 2