It's in the town with the fourth gym leader.
In Third Generation Whirlpool is no longer an HM.
If you go to Mt. Mortar, this guy will bump into you so to say sorry he will give you the HM Strength.
In the Cave of Origin.
up your rump
there is no such move as stength
You get the hm strength and give it to one of your pokemon
it isn't in Pokemon platinum its in ruby and Sapphire
in the cave of origin
Use the hm surf
in the cave of orgin
Get the HM Rock Smash
Actually, you can't get HM Rock Climb on Pokemon Ruby, its only available in Pokemon Diamond, Pearl and Platinum.