external drive rw via finder but cannot read from cmd line

Glad you were able to figure out a solution. You can also press the Tab key (sometimes you need to press the Tab key twice in a row) which will try to auto complete the command or path or it will show you the possible options. So if you begin by typing:

ls  -al  /Volumes/

then press the Tab key (one or two times maybe) and it will show you the items you can select in the "/Volumes" folder. Typing more characters and pressing Tab again will narrow down the options even further:

ls  -al  /Volumes/MI

You can also begin typing (make sure to leave at least one space after the "-al "):

ls  -al 

and then dragging & dropping the mounted volume from a Finder window onto the open Terminal window which will auto complete the correct path.

If you want us to assist you with using the command line to access the drive, then we need to see the actual command(s) you are using and the results. We also need to know where the drive is mounted. macOS no longer allows users to access the system area of macOS so you need to either use the default "/Volumes" location to mount the drive or mount it somewhere in the "/Users" folder.

I keep forgetting about this bit of added security. Thanks for adding the extra tip.