If you are searching for a DMG download of iMovie 10.2.5, you are likely looking for a standalone installer rather than the standard App Store update.
If you cannot access version 10.2.5 through Purchased history, consider updating your macOS to at least 10.15 (Catalina) to run iMovie 10.3.9+, or use as a free, powerful alternative for older Macs. Imovie 10.2.5 Download Dmg
The modern Mac App Store automatically serves the latest iMovie version (10.4+). However, if your Mac is stuck on an older OS, the App Store will offer you the final compatible version — which might be 10.2.5 or slightly newer (10.3.x). If you are searching for a DMG download of iMovie 10