The app is called Filebox, an interesting name.
Go to this link below from the ovi store from your Nokia N9 via ovi store application which comes pre-loaded on your phone and install the app.
http://store.ovi.com/content/204982
Once installed you can see on your home-screen. Click on it, you will see how it looks below.
Here are some settings from the filebox app.
About Filebox
Some more screen-shots
Not only you can manage files on your N9, but you can compress files on it too.
I compressed a mp3 file to zip format easily. I compressed a 10MB Mp3 file to 8MB.
You can now manage your files and folders more efficiently on the N9.
