Usually we format removable disks like pendrive and external HDD from windows. Just right click on the drive and click format option as shown in below pic.
If your system is infected with virus it will disable right click. Then you can’t format removable drive. In such cases you can format removable disk from command prompt. The same procedure applies to usb stick and external HDD.
Steps to Format Removable Disk from Command Prompt
Open Run, type cmd and hit enter as shown in below pic.
In command prompt type format Drive Name: as shown below pic.
It verifies for the contents of the disk.
After verifying it asks for the volume label as below pic.