Gparted is the software for formatting USB pen drive in ubuntu with simple graphical user interface. It can be installed from ubuntu repositories by Synaptic Package Manager.
Alternatively, it can be installed by giving command in terminal:
sudo apt-get install gparted
Insert USB drive, right click on it and select unmount. Now open gparted by giving command in terminal:
sudo gparted
select the pen drive carefully from gparted>>devices
it will show like:
/dev/sda (149.05GiB)
/dev/sdb (249.79MiB)
as in my case for 256MB pen drive it is showing /dev/sdb (249.79MiB)
after selecting click on Partition>>format to>>fat32
click on Apply to Format.
