I had some issues formatting my USB external drive on the Pi.
For large hard drives, use parted. I'm old school, so I defaulted to trying to use fdisk. It would stall out at 100% CPU and just sit there. I ended up using parted on another linux box to partition the drive, then I formatted it using mkfs.ext4. After you format the drive, and plug it in, it'll automount to /media/pi/somereallylongUUIDnumber
To mount the drive to a specific location on the Pi, once the drive is auto-mounted, use blkid to view the UUID of the drive, then use that UUID in the /etc/fstab:
/dev/sda1: UUID="5dfc9465-37cb-49c5-bd01-5dc5d033ef1b" TYPE="ext4" PARTLABEL="ORCHID"...
Use the UUID above and edit your /etc/fstab:
UUID=5dfc9465-37cb-49c5-bd01-5dc5d033ef1b /ORCHID_DATA ext4 defaults,errors=remount-ro 0 1
Now, when you plug in that USB drive, it will automount to /ORCHID_DATA (I created this directory, you can name it whatever you want here)