If GameObject with tags not on scene

I work Unity 4.3. I have coins object on scene. They have tags: ,Coin". (These are prefab) I will make this: if all ,Coin" tagged object destroyed on scene, then activate Level2. How can I make this?
I have this code in a simple GameObject on scene, but does not work.
If play scene, all tagged coin in scene, but the level2 activated…

if ( GameObject.FindWithTag("Coin") !=null)
 {
 Application.LoadLevel ("Level2");
  }

This does not work too:

if ( GameObject.FindGameObjectsWithTag("Coin") !=null)
 {
 Application.LoadLevel ("Level2");
  }

Try this:

if ( GameObject.FindGameObjectsWithTag("Coin").Length == 0)
{
    Application.LoadLevel ("Level2");
}

You cannot use a null check because FindGameOjectsWithTag() always returns an array. It just will be empty if it does not find anything.

Or alternately you can do:

if ( GameObject.FindWithTag("Coin") == null)
{
    Application.LoadLevel ("Level2");
}

FindWithTag() returns the first one found, so null check will work here.