What is the value of a Pip?

I see some currencies have four decimal places and some have five. If I wanted to apply a MM strategy and set an S/L I would need to know the risk. I would like to use something like a 2 to 1 ratio whereas my S/L would equal 50% of my target price. But, I can't figure out the value of (1) Pip. Typical newbie question, but hope someone will answer.

Thanks