Valleys is the only way to make the noun valley plural. Confusion arises because some people mistakenly believe that all nouns ending in "y" should form a plural ending in "ies".

What is the correct spelling of valleys?

noun, plural val·leys. an elongated depression between uplands, hills, or mountains, especially one following the course of a stream. an extensive, more or less flat, and relatively low region drained by a great river system.

What is valley plural?

noun. val·​ley | \ ˈva-lē \ plural valleys.