I'm sorry but I've been trying to find the place where you pan for like a long time ;-;
The stream in camp past the elders den! Then just go into your inventory and press the pan thing, click/tap use, and click/tap on it once it’s above the river. Then when it comes back up just keep pressing it until it’s shiny or you see a message on the top right of your screen saying something like: You got tin!