What do you need for the treasure maps?
Watching this YouTube video, it does not seem like you need any special item. Instead, there should be a special dirt mound that you can interact with by pressing the "Use" button on it. Upon digging the pile of dirt up, the treasure map will removed from your inventory and you will receive your treasure.
The mound of dirt in this case looked like a grassy mound with some rocks on it. I assume it would look either like this, or similar to this:
