Once opened, go to iMovie > About iMovie in the menu bar. You should see and the build number (e.g., 12473).
However, if you own a Mac from 2015 or later, You should install macOS Monterey, Ventura, or Sonoma via OpenCore Legacy Patcher and run the modern iMovie. The "1025" update lacks modern features like 4K timeline support, 360-degree video, and magnetic timeline improvements. imovie 1025 dmg upd
It looks like you meant (the ".2" and "5" are often typed close together or missed). Here are a few options for the post, depending on where you are posting it (e.g., a tech forum, social media, or a software update log). Once opened, go to iMovie > About iMovie in the menu bar