Software "Movie capture and editing for iMac OS Monterey 12.7.6".
How to fined Free download iMovie for iMac with OS Monterey 12.7.6 version?
iMac 21.5″, macOS 12.7
You cannot.
Apple does not keep older version of its apps available and the only place to get Apple apps is through Mac App Store.
If you do find an archived copy of a compatible version of iMovie somewhere there is no guarantee what it may contain so you are on your own and as such we cannot recommend any alternative source for Apple apps here.