Set up iCloud Drive on your iPhone
In addition to using iCloud Drive on iCloud.com, you can work with your files and folders stored in iCloud Drive on your iPhone and other devices.
Important: Your devices must be set up for iCloud Drive and meet the minimum system requirements listed in the Apple Support article System requirements for iCloud. You must also be signed in with your Apple ID on each device.
If you have devices with iCloud Drive turned off, documents and data on those devices aren’t kept up to date with documents and data on your devices with iCloud Drive turned on.
Go to Settings > [your name] > iCloud.
Turn on iCloud Drive.
You can view your files in the Files app. If you don’t have the Files app, you can get it from the App Store.