What you exactly need to get the TM37 Sandstorm, how many ways there are and where it is located, are explained in more detail in this article.
Pokemon Brilliant Diamond & Shining Pearl – How To Get TM37 Sandstorm
So at the beginning, I should mention that we have 2 ways to get to TM37 Sandstorm. Don’t worry though as it is quite simple.
The first way is to go to Pastoria City. Use the Explorer Kit, click “Play alone” and it will take you underground.
You will find this TM 37 in a room marked on the map as shown in the picture above.
When you enter the room, watch out for the pokémon that will chase you. Go to the upper left part of the room and among a few rocks, you will find the TM37 Sandstorm.
The second way is also in Pastoria City. From the Pokémon Center go to Route 212. You will know you are on Route 212 when you notice the rain.
When you come across the two small trees, cut them down and climb the stairs. From here you will have a wooden plank that leads you to the north.
Then head west between the trees and after a while, you will reach the Shard house. Here you can replace the shard for TM.
And these are the two ways you can get to the TM37 Sandstorm. So pop right into Pastoria City now and claim it!