Hello pjewing,
Thanks for asking the Apple Support Communities for help with getting the files on your Dell to update with iCloud.
1. When you have iCloud for Windows, you can add files to iCloud Drive. This article talks about iCloud for Windows: Set up and use iCloud for Windows - Apple Support
2. To add files, you use Windows File Explorer. This article talks about this: iCloud: Use iCloud Drive on a computer or iOS device - Apple Support
"On a Windows computer
- Open File Explorer (Windows 8 or later) or Windows Explorer (Windows 7), then click iCloud Drive in the sidebar to see all your files and folders in iCloud Drive. Add files to folders, create new folders, and reorganize folders as you would on the Windows desktop. To copy files to your computer, drag them out of iCloud Drive to the desktop.
You can work with your iCloud Drive files on an iOS device using the Files app (or the iCloud Drive app on iOS 10 or 9). See the iPhone, iPad, or iPod touch user guide for more details. For a device that doesn’t have the latest version of iOS installed, you can download the user guide from the Apple Support Manuals website."
3. Also, please ensure you have enough iCloud Storage. Without enough space, your files may not update. Manage your iCloud storage - Apple Support
"If you run out of iCloud storage, your device won't back up to iCloud, new photos and videos won't upload to iCloud Photo Library, and iCloud Drive, other iCloud apps, and your text messages won't stay up to date across your devices. And you can't send or receive emails with your iCloud email address. If this happens, you can make more space."
Thanks and have a wonderful day.