A Pickaxe is an item found in Pajama Sam in No Need to Hide When It's Dark Outside.
Sam will need the pickaxe in order to gain access to the park. Sam will find the pickaxe next to the secret entrance to Darkness's house. When Pajama Sam picks it up, King warns him to be careful with it. When Sam finds the location of the gold, he will need to use the pickaxe to mine the gold. He accidentally breaks it, but luckily he manages to obtain two gold nuggets, one of which he lets King keep.
Doing this is optional, unless Sam needs to get his flashlight from the mines.