BrandiQuiksilver says:
what type of strings are best for acoustic guitar? how much would you pay for strings? how would you tune it right?
So it's really going to depend on if your guitar is a classical guitar or steel string acoustic.
I don't think nylon strings have a ball on the end so I don't see how you can convert a steal string into nylon string.
Most decent acoustic guitars are going to work fine with string gauges 9-12 with out any modifications.
If the guitars setup is good then I'd go with the higher gauge strings I feel they have my dynamics as well as volume. However they will be 'tighter'.
I'd hit up your local music store and find the a guitar player and ask for a recommendation.
I save my string wrappers so I remember what strings I like/don't like. My last set of acoustic strings were D'Addarop Acoustic Guitar Ligth EXP16 .012-.053. They are coated and had a great bright tone.
I've never really cared much for the guitar makers brand strings such as martin, fender, gibson etc.
I hope that helps