Q: How do you manage files/folder on an iPad3 (like Win/Mac file/folder explorers)???

The iPad doesn't have a file system like a 'normal' computer, everything has to be associated/stored within an app - so there is no need for anything like windows explorer, you manage each app's content from within the app.

In terms of external storage, the camera connection kit allows you to copy photos and videos to the iPad's Photos app (but not to copy content to other apps or to copy content off the iPad), and there are some wifi-enabled drives that allow you to stream content to the iPad.

You can store them on SD cards, but you will need to copy them to the iPad (which you can do via the kit to the Photos app) in order to play them - you can then delete from the iPad when you've watched them.

I have managed to copy an MP4 film via an SD card with the kit and been able to play it, but a film bought from iTunes didn't play (you can't copy content to the Videos app via the kit). Also the kit only recognises content that is in a particular format - the card has to have a DCIM directory off its root, with the photos/videos underneath it with filenames exactly 8 characters long (no spaces) plus file extension.