Three dimensional arrays are very similar to two dimensional.
int[, ,] Array3d = new int[2, 2, 3] { { { 1, 2, 3 }, { 4, 5, 6 } },
{ { 7, 8, 9 }, { 10, 11, 12 } } };
Debug.WriteLine(Array3d[0, 0, 0]);
Debug.WriteLine(Array3d[0, 0, 1]);
Debug.WriteLine(Array3d[0, 0, 2]);
Debug.WriteLine(Array3d[0, 1, 0]);
Debug.WriteLine(Array3d[0, 1, 1]);
Debug.WriteLine(Array3d[0, 1, 2]);
Debug.WriteLine(Array3d[1, 0, 0]);
Debug.WriteLine(Array3d[1, 0, 1]);
Debug.WriteLine(Array3d[1, 0, 2]);
Debug.WriteLine(Array3d[1, 1, 0]);
Debug.WriteLine(Array3d[1, 1, 1]);
Debug.WriteLine(Array3d[1, 1, 2]);
Try the above code.
This is very basic way of implementing three-d arrays. for more complex purposes, different data structures can be used to implement three-d arrays.
Hope this is useful.