why captain billy bone was finding Long John Silver

I'm not sure what you are meaning. What chapter are you referring to?

I think I can help you. The reason why Billy Bones is asking Jim to lookout for the "one legged man" is that Long John Silver had sailed with Flint's crew before- just like Billy Bones. He probably needs the map to search for the lost treasure while Bily Bones does't want to hand it over. Maybe? I'm sure you are reffering to chapter number 1. Well, I tried to help.