''Do or do not. There is no try'' Trophy in LEGO Star Wars: The Skywalker Saga
''Do or do not. There is no try''
Complete all Galaxy Challenges
How to unlock ''Do or do not. There is no try''Galaxy Challenges are a series of challenges that aren't tied to a specific planet or area, and require hopping between multiple locations to find, destroy or complete specific objectives. They can be found and tracked through the Missions tab, and tracking them will give you a general location of where to go to find the things you're looking for.
In the specific case of the challenge for destroying Mouse Droids with helmets on them, I found that the location given by the tracker wasn't always completely accurate. Use that as a general guide, and then broaden your search until you see the droid, or you see a red dot moving quickly on your mini-map.