So, go to the pin that you are wanting to know more about. In this case, I want to see where this Landforms activity has been pinned so that I don't pin it in the same place again.
Click on the picture to make the pin bigger and NOT the repin button.
Of course, you can always go to your own Pinterest dashboard and click the pins link to see where YOU have pinned your pin personally. But in this case, you are now seeing where OTHER people have re-pinned for you.