For Doing this we need a Software which you can download from the link below :
Click Here To Download
Step 1: After Downloading the software, install it on your Operating System.
Step 2: Open the Software and Insert the Pendrive in which you want to erase the data permanently.
Step 3: A Window will be displayed like this.
Step 4: Click on the Tools Menu and Select Drive Wiper option.
Step 5: In the Wipe menu select Entire Drive(All Data will be Erased) option.
Step 6: In the Security menu select Very Complex Overwrite (35 Passes) option.
Step 7: In the Drives menu select the drive which you want to get formatted.
Step 8: And Finally click on the Wipe button and take some rest because it will take a lot of time to overwrite it.
In the Drives menu don't select your hard drive.