It will fit onto the bottom mount on your NEX-3 but that is all you will be able to do.
There are two types of shoes you can get.
Hot shoe - has an electronic connection between the mount on the bracket where the flash sits and the body can fire the flash through this shoe.
Cold shoe - has no electronics and is simply a place to mount a flash but cannot be fired.
Ideally you need a hot shoe mount but none are available for the NEX series.
Hope that helps
