Hi! i am a little confused by your question, but I think what you were saying is that you are estranged from your father or something and trying to locate him and you know he is a nurse but you don't know where. Am i correct in that, or did I totally miss the meaning of your question?
Assuming that is what you are trying to do, I would go about it like this IF he is in the United States. I don't know how to search outside of the United States.
I don't know of a SINGLE registery in the United States, but EACH state individually has a list of all their registered nurses and licensed practical nurses. It may be a bit time consuming if you don't know which state he is in, bt you can do each one at a time. Hopefully, you know if he is an RN or LPN/LVN, or it will be double the inquiries.
I believe all the states list these online as well. I have been able to look it up for any state I have worked in or planned to work in and always found this list.
Just Google for example, "Florida State Board of Nursing", or whatever state you are looking in and there is a search feature for all professional licenses that you can search by name.
I hope I understood your question. Hope this helps and best of luck in your search.