I have a flash drive with all the files from my old PC. How do I access / find this flash drive after it is installed, and can I save and use these files (Microsoft Word, Excel, PowerPoint, Outlook primarily)?
I'm going to assume you are talking about finding it in Terminal and not Finder as you asked about access /.
That will put you in the / directory of the flash drive. If you don't know the name of the flash drive.
Then do a ls. Your flash drive should be listed. You could also find the name of the flash drive listed in Finder.
Accessing Flash Drive
You have a number of options here: