I used all of the 2TB. What is the next upgraded storage plan?

2TB is the largest plan available unless you also subscribe to Apple One. See the following from What happens to your iCloud storage when you sign up for Apple One - Apple Support

If you need more iCloud storage

After you subscribe to Apple One, you can buy more iCloud storage if you need more. With both Apple One and an iCloud+ plan, you can have up to 4TB of total iCloud storage.

tbterfa Said:

"I used all of the 2TB. What is the next upgraded storage plan?"

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Try Downloading All of iCloud:

Download all of iCloud. Then, verify your can access what has been downloaded. Once verified, trash what is in there. Search for files through use of Finder in a window. Perform my User Tip: Getting a Quick and Direct "iCloud Drive-to-External Hard Drive" Download - User Tip