visitation. .

So I have a friend who was wondering how he could get visitation and be able to contact his 5year old daughter. His ex moved to a different state and she didn't tell him where they moved to.. won't let him see their daughter or talk to her. She blocked him on social media as well so he can't even see pictures of her.. I know he misses his daughter a lot and hasn't seen or talked to her in 3 years.. does any one have any advice on how he would go about trying to change any of that so he can see/talk to his baby again?