Hi morganmusic1,
Thanks for contacting Apple Support Communities!
We understand that you're attempting to upload a video to iCloud for Windows, correct?
iCloud for Windows allows you to access your photos and videos from your devices. You can upload JPEG images via iCloud.com from your computer: Upload and download photos using iCloud.com
You can learn more about iCloud for Windows features here: What is iCloud for Windows?
"iCloud Photos, iCloud Shared Photo Library, and Shared Albums
iCloud Photos automatically and securely stores all your photos and videos, and keeps them up to date on all your devices and on iCloud.com. Learn how to view photos and videos."
We hope this helps.
Cheers!