Adopting a Cousins

Hi, my name is Nelson. I am on a process of adopting my Sister's Cousins (two girls,ages 14 &16) from a foreign country. I am a Citizen and my Wife just completed her citizenship interview. My cousins were added on my Wife Citizenship application initially. they got approve and when she sat her interview. She recently flew over to the foreign country (Liberia) to get my Cousins adoption documentations. The process was successful, but the foreign country is asking us to send Report of Home Study from us in the United States. My question is, how do we go about getting this process complete? Which Agency is responsible for this home study, please provide us some names. I live in North Carolina. I will appreciate it if you have any advice for us.