Let’s talk about a little less complicated and a casual way though powerful enough to get the job done. Yes we’re considering a task to format or perhaps make a bootable drive USB here, for command line freaks you may read here.
Gparted the Gnome by defacto tool for disk related chores for Joe, Tom and folks a like a tool so powerful which can even make a newbie & a seasoned user more confident, before doing any changes to the core system.
I’ve used this tool for a decade now and as of now testing on my Eoan Ermine, Gnome 3.34 the latest at the time of writing and I’ve already installed it via the default Ubuntu Software, but you may get the package from elsewhere that’s fine as far as it’s stabe and does the work for you. Snap pack, Fine ! Flatpak, Cool!! .deb package, shall do = > Your mileage may vary Joe.
Now let us get into the business, insert your external flash, usb or pen drive and just let the tool run, after that select the drive via dropdown from the top left hand corner and you’re good to go.
Now just select the partion wherein you wish to erase as per se format and select via GUI those comfortable anxiety free buttons and keep rolling.
Enjoy ! rest all is self explanatory, the tool is intuitive in itself IMO.