Transfer Files From Hidden HDD Macintosh Volume to USB in Recovery Mode From Terminal

Ok. I am not particularly tech savvy. I am trying to transfer the contents of 2012 Macintosh HDD to a USB drive. My computer crashed and I am trying to recover some files from the Macintosh HDD Volume in the Recovery Mode Terminal.

1. The volume is unmounted and I cannot mount it
2. When I type pwd I get ‘/volumes’
3. When I type ls -a I get ‘.Trashes’ ‘EFI’ and ‘OS X Base System’
4. The volume is non repairable
5. diskutil list does not give me a UUID

So, What I am trying to do is reveal this volume, navigate to it, and extract the files.

For the purposes of this question, revealing and accessing the volume are what I am trying to do, as I think I can work out how to copy and paste files once I am in. Just hoping the files are still available in the corrupted volume.

Thanks