Retain Un allocated space in USB drive

C:\Users\New Tech>diskpart
Microsoft DiskPart version 6.2.9200

Copyright (C) 1999-2012 Microsoft Corporation.
On computer: NPLP05

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online          465 GB      0 B
  Disk 1    No Media           0 B      0 B                                 //this is dvd/cd ROM
  Disk 2    Online           14 GB      0 B

DISKPART> select disk 2

Disk 2 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

Leaving DiskPart...

C:\Users\New Tech> / // the partition of usb drive is in FAT by default