Where is the camp store?
Solution 1:
The Camp Store is inside the lodge, which is in the "Main Campgrounds" zone of Whispering Rock:
It's just to the right as you enter the lodge.
Solution 2:
The camp store is inside the lodge. Agent Cruller is inside in a chef's hat and apron, and if you talk to him, he will let you know what you can buy. What you can buy depends on your rank - as you reach a higher rank, you will be able to buy more items.