First, come to the listed coordinates.
Afternoon would be the best.
Your journey starts here.
Walk to the north,
Especially on your right.
Have you found "the Moon"?
All right, good!!
Now, open the door to say "Hello!".
You are in the Moon and about to complete the mission.
Next, look immediately to your left on the wall.
Find a 3x3 matrix (or grid).
The cache is right in the center.
Have a nice afternoon!