Legal Question in Family Law in California

Re: How do I answer a petition to modify the child custody and visitation order?

The family court should have a law clinic that will provide help. Also contact the local bar association and ask about free legal assistance or low cost legal assistance. Your response would depend upon a large number of facts. Among them is why was he in prison, was there domestic violence, how old are the children, etc. You would have to discuss the facts of your case with an attorney. That process is too lengthy for the internet.