For what reason did Jim ride with Dogger to see Dr.Livesey?

I think this is what you mean,

Jim tells the men that he has a packet, something that he believes that the pirates were searching for, the oilcloth packet of papers, and that he wants to give it to Dr. Livesy for safekeeping. Supervisor Dance, the leader of the men, take Jim up on the horse of one of the riders to accompany them to Livesey's.