The questions aren't stored in files, as such. They are stored in your database engine on the server. If you have root level access to the server, you could see the files that MySQL stores the info in, but the files wouldn't be in a format you could use for anything else, or even read. It would be much better to use something like phpMyAdmin to export a list of the questions you want into a CSV file, which you could then use for whatever you are planning.
Just out of curiosity, what did you need access to those for anyway? It is very unusual to try an access them directly.