How do you get the hm move strength in diamond and pearl Pokemon for ds?

In Diamond and Pearl versions of Pokemon, the HM move Strength can be found on Iron Island. To proceed:

1. Travel to Celestic Town and talk to the Sailor next to the sailor who lets you sail to Fullmoon Island with the Lunar Feather.

2. He lets you board the S.S. Strength, which takes you to Iron Island.

3. Follow the path. Along the way, you'll need to solve a puzzle with several boxes.

4. Inside the cave to the North of the building on Iron Island, you will find the TM for the move Strength as well as a Pokemon that can learn the move.