Do I need a 2 or 3 pin plug ????
It all depends on what socket is on the wall and what you are intending to plug in.
I use the 2 pin plugs to charge phones, Ipads, batteries, etc. If you are trying a device that pulls a lot of current, i.e., hairdryers or straighteners, cooking devices, etc., you may want the 3 pin.
The third pin is a ground.
2 pin plugs unless you are bringing something like a laptop.
You may want one of each. I have been in some hotels that didn't have any 2 prong outlets. The reverse also might happen. Nothing more frustrating than not being able to charge anything.