Added a 4th Bedroom to rental - How do I get appraisal to reflect

[Douglas Rice]

I bought a 3/2 single family in 2016 and converted it to a 4/2 prior to renting it in 2017. I was sure to add a closet so it can be counted as a 4th bedroom. I also closed off an open area and added french doors to make an office. 

a 3/2 in this neighborhood with the same sq ft is about $275k and a 4/2 is about 300-315K. The county shows it as a 3/2 on record. How do I go about ensuring this will appraise as a 4/2 and get the value I am looking for? Do I need to file anything with the county to make it official or will an appraiser just see the 4th bedroom and use similar comps?