You get HM strength in the lost tower, which can be found south of Solaceon Town. Talk to an old lady in the 5th floor and she'll give the HM strength. But be4 you can use it, you must have the sixth gym badge, the canalave badge. Hope this helps.
iron island
top of the tower in solocean
get the HM strength, and teach it to a Pokemon
I think it is strength
You have to get strength, and teach it to your pokemon. It is so easy a caveman can do it.
Solaceon town is the where the tower is located in which the player can find the strength HM. This town is located off of route 209 in Pokemon Diamond and Pearl.
top floor on the lost tower
you mest get the hm strength.
near this house in the snow down from snowpoint
You need the cobble badge.
First you find the HM in the lost tower next to the hollow tower. then you get the badge from canlave city and your Pokemon can use strength
The HM strength