How can I recover a USB drive that now shows 0 MB after formatting?

Since the USB was empty, there aren't any files to restore from a backup. The important thing is to stop selecting random options and read each step before confirming it. If DiskPart cannot see the correct capacity or reports errors while cleaning or creating a partition, the flash drive itself may have failed rather than just having a damaged partition.

If you're using Windows and don't need anything on the drive, you can usually recreate its partition table with DiskPart. Open Command Prompt as administrator, run `diskpart`, then `list disk`. Carefully identify the USB by its capacity—don't guess if another disk is similar in size. Run `select disk X` with the correct number, double-check it, and then run `clean`. This removes all partitions from the selected drive. Afterward, open Disk Management with `diskmgmt.msc`, initialize the USB if prompted, create a new simple volume, and format it. Be extremely careful because choosing the wrong disk will erase that disk.