TEPNU's Treasure

TEPNU lost their treasure somewhere nearby. So they decided to start looking for it with the help of their friends. They found the treasure box but forgot the code to it! TEPNU looked up into the sky and started to think... What was the number... Then, three clouds formed overhead, aha thought TEPNU! It's the number 3. TEPNU put the key with #3 on it into the box and voila! It popped open and all their treasure was safe inside.