iMovie for an older operating system and "new" computer to me

Looking for some help and hoping I'm not just out of luck. I purchased through a government auction an iMac all-in-one running Catalina 10.15.7 for the purpose of running iMovie. Unfortunately it does not have iMovie on it, and I'm trying to figure out if I'm now just out of luck or if there is a way I can get the version of iMovie that will work on it. I have had a couple Macs over my years but I did not have to download iMovie to them, it was part of the original software package. I have checked my Apple account for downloads to see if I can get iMovie there and I do not have it available. I looked at the Hidden items, again nothing there. Is there any other way I might get the iMovie needed for this Catalina 10.15.7 system or am I really just dead in the water.

Thanks for any help you might provide, I appreciate it.

And if I am screwed so to speak, any suggestions on video editing software that will work well with this Catalina 10.15.7 system? I have used DaVinci Resolve and it's just way more than I need. Capcut was okay but also wasn't great but I did use it on a different computer so maybe it was more a computer issue. Anyway, taking suggestions if I am just stuck here with my new gov't auction paperweight.