#first check the usb drive 
lsblk
#then -> if= is source and of= is destination/the usb drive name
# you got from lsblk that have the usb drive
dd bs=4M if=/tmp/ubuntu-20.04.1-desktop-amd64.iso of=/dev/sdc conv=fdatasync
#Where bs is read and write BYTES bytes at a time,
#if is the input file, of is the output file. 
#The conv=fdatasync bit is important as dd 
#can return before the write operation finishes.