multiple of 3 in a set of given array

public void GetMultipleOfNumber(int[] Array, int Number)
{
    //Code
}

You can do this on your own, can't you?
Its easy, the method head is given.
You just need to iterate (for-slope) through your array.
Then do a modulo on that! (Array[i]%Number).
If the modulo returns 0 it's good (E.g. 15%3 = 0)
Then you can do with the result what you want.

Finished. Basic stuff. Homework...