I am not able to format my pen drive itz appearing that make sure no window is using the device

Try this method.
insert pen drive into usb
open up my computer
right click on the pen drive and format.

sometimes when you have the folder open that you want to format it wont want to do it, so by opening up my computer and only right clicking on it, you wont be accessing any of the data on there you will be just telling it to forrmat it.

that failing you might need to search for a pen drive utility that combats these issues specifically.

Install Unlocker. Right click on the drive and select Unlocker. If a list appears, click on "Unlock All". Now format your drive.