Korean adoptee searching for birthfamily, adopted May 2, 1976

I am searching for my birthfamily in Korea. I was adopted on May 2, 1976 through a charity organization from an orphanage in Seoul Korea. My greencard says I was born on 4/1/72, however I believe I was born in 1969. I arrived at Minneapolis, Minnesota. Can anyone help. I believe my father and siblings are still alive and possibly looking for me.