iMovie 9 for OS Yosemite

Hi All, I have a MacBookPro with Yosemite still on it (10.10.5) and would like to use iMovie. The most recent version does not work on this old operating system. Any clues how to ge the old iMovie?

I do regular Time Machine back ups and I see and iMovie App Download in my folders but not the Application itself so when I try to bring it to the laptop, nothing happens.

Advice welcome! Thanks in advance.