copy folder via terminal from usb start up

I have an older macbook pro (2009 / 2010 gen) which on this last OSX update High Sierra 10.13.3 never made it back to a login screen after being restarted. After about 20min of going though the start up progress bar it just stops working. I left it overnight last night just to make sure it didn't just need more time to update. Thankfully I have a new macbook pro I use for work. I've created a bootable usb drive and bingo I'm in to disk utilities start up mode. I run a first aid check on my Macintosh HD no errors everything should be a go. so I restart put my 3T My Book drive in, it's showing up under external. So I know it's reading. I have 1 folder on the desktop named My Stuff. My question is can I copy that folder to my book external via terminal? I found one that said to do this via terminal:

[-bash-3.2# (this is what terminal starts with on the screen) then I type...

sudo cp -R /My/Book /Desktop/My/Work

I get this in return:

-bash: sudo: command not found

Is there another way of doing this? are my commands wrong? any help would be appreciated.