If you want the folders to show the number of files read the old thread on the forum about how to show the file count.
It says to install the fox plugin
https://addons.mozilla.org/en-US/firefox/addon/stylish/ and then go to Tools in Firefox, then Add-Ons, then Extensions, find Stylish, then edit and then paste the script below. Also give it your script name.
Click "save" then restart Firefox.
.v-FolderSource:after {
content: " " attr(title);
font-size:12pt;
}