Just start calling, that's what I did. I called Millhaven and the guy I spoke to there, was alright. Really, they aren't allowed to give inmate details. If you have a lawyer, he or she can find out on your behalf. Is there a deeper reason as to why you don't know where he is? Is he estranged?
You can pm me with any questions. I'm glad to help in any way that I can.