Adoption records are not available to the public. After the records are sealed at the time of adoption, you have to get a court order to open them.
Adoption records in New York State are kept in the Family Court or Surrogate Court where the child was adopted. You should contact the Adoptions Clerk of these courts in the borough where you think the adoption took place.
You can also register with New York State's Adoption Information Registry. The registry does not release adoption records, but it can provide general information about birth parents and the name of the agency that arranged the adoption. If all parties register, the registry can help parents, children, and siblings reunite.