I'm sure there's a better way, but here's a (hopefully) foolproof one ...

Create a file called path.php with the following contents
PHP Code:
<?php
  echo $_SERVER['SCRIPT_FILENAME'];
?>
Put it in your store's root folder and then run it via a browser.
It will give you the full path on the server to the file, so removing the filename will give you the answer you need for your configure files.