Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Nŭmistro, ōnis, f., a city in Lucania, near the mod. Muro, Liv. 27, 2, 4; Front. 2, 2, 6.
Hence, Nŭmistrāni or Nŭ-mestrāni, ōrum, m., the inhabitants of Numistro, Plin. 3, 11, 15, § 98.