i have a s-s-h type yammaha and I was wondering how to convert it into a single humbucker with just a volume knob
Well, the most basic thing you need, and really the only one, is a new pickguard. I think websites like pickguardheaven.com have em, i would do a google search about it. You may need a custom one. While your at it, I would buy a new, better humbucker and a new pot as well, altho those are optional. Check some place like the Duncan pickup website for wiring diagrams, it should be easy to find.
Look on guitarfetish-they have the exact thing you're talking about. Of course, it's meant for a real strat, not a pacifica (not that pacificas are bad-quite the contrary), so some filling and drilling may be needed.