Recovering unallocated space of a USB flash drive

Run CMD (Command Prompt with administrative rights)

type diskpart

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  ——–  ————-  ——-  ——-  —  —
  Disk 0    Online          298 GB      0 B
  Disk 1    Online         7509 MB  6619 MB

DISKPART> select disk 1

Disk 1 is now the selected disk.

DISKPART> clean

DiskPart succeeded in cleaning the disk.

DISKPART> create partition primary

DiskPart succeeded in creating the specified partition.

DISKPART> exit