@Rudy-Trujillo @Kit-Bishop is right. I didn't see this before, but the first picture you showed might be wrong:
It says it has mounted /dev/sda as /overlay, whereas it should be one of the partitions under that drive, i.e. /dev/sda1.
You should try to use a partitioning software such as fdisk or gparted to first create a new partition on your USB drive, and then issuing mkfs.ext4 on the newly created partition. That should be able to solve your problem.
Please let me know if you have any other questions.