What does Mōns Ferrātus mean in Latin?

Mōns Ferrātus, a proper noun, means “Montferrat (a historical region in modern Piedmont, Italy)”.

What is the genitive of Mōns Ferrātus?

The genitive singular is Montis Ferrātī. Mōns Ferrātus is third declension.

proper nounthird declension

Mōns Ferrātus m sg (genitive Montis Ferrātī)

Medieval LatinMontferrat (a historical region in modern Piedmont, Italy)
[…] in Monteferrato in loco qui dicitur Rivassi mansos quinque cum insula infra Padum […][…] in Montferrat, in a place called Rivasso, five manors, with an island below the Po […]909 June, Berengar I of Italy, [untitled bill]; republished as chapter LXIX (chapter 69), in Luigi Schiaparelli, editor, I diplomi di Berengario I, Rome: Forzani & c., 1903, page 187:
[…] & omnia, que in Monte Farrato, & que in Comitatu Vercellenſi & Yporegienſi, & que in Novarienſi ad eundem locum pertinent […][…] and those which, in Montferrat, and in the county of Vercelli and Ivrea, and in [the land of] Novara, relate to that same place […]1033 February 23, Conradi I imperatoris privilegium confirmatorium omnium iurium monasterii Ticinensis sancti Petri, quod appellatur in Cœlo Aureo [Bill of Emperor Conrad I in confirmation of all rights of the monastery of st. Peter in Ticino, called "in the Golden Sky"]; republished in Ludovico Antonio Muratori, editor, Antiquitates Italicae medii aevi [Italic antiques of the Middle Ages], volume 1, Milan: Typographia societatis Palatinae, 1738, pages 595–596:

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