Downloading iMovie
You could download iMovie from the App Store in 2020, and if you are using an older iPad, I recommend you download iMovie first on newer iPadOS device. Then, open the older iPad, and open the App Store. In the apps store, you could see a 'Purchased' bar or 'Purchased' bar in the Updates section. If you are using iPadOS 13 or later, click on your Apple ID icon on the top right corner of your screen. Click purchased, and click on My Purchases. Search or find iMovie there. Anyways, no matter which iPad OS you are using, click on 'Purchased' and search for iMovie. You should have it there. When you click the 'cloud' sign, that means you are downloading the app from iCloud. Click on 'Download' after a banner that says 'do you want to download a previous version of this app?'. And there you have it!
To my devices, iMovie did not download in previoud iPads. I don't know why, but i tried several times.
Sincerely
Will
iPad 2