Translating a phrase

Hi, I'm looking for an elvish translation of "Return of the mearas" but I can't seem to put it together. Could someone please help?

A clarification: "Elvish" is a term that encompasses multiple languages which Tolkien made for different Elf groups. The most important of which are called Quenya and Sindarin. View this FAQ post on Reddit for more information on them. I will try and provide a Sindarin translation, since this is the most commonly spoken Elvish language in the books.

Sadly, translations for neither "return" (as a noun) nor "mearh (singular of mearas)" can be found in the notes of Tolkien for Sindarin. However, a neologism (based on the ancient Elvish root √RAD "to return" by him, derived with his phonetic rules) in the form of *raudh could work as "return". And I would personally translate "mearh" as "noble-horse", thus *arroch. Finally, pluralising it to *errych, I would offer:

Raudh Errych
"Return [of the] Noble-horses"

(The genitive element "of" is implied by word order, and the article "the" can be omitted, hence in brackets.)

That's fantastic! Can you help me with pronouncing it?

The "r" in raudh would be a "tapped r" (click for voice file); Tolkien described "r" in Elvish languages to be generally "rolled r" but he pronounced "tapped r" in certain positions. The "au" is read like in the word "now" (here is a video on it). And the "dh" is the same as in "that" (click for voice file).

The double "r" in errych needs to be rolled (click for voice file), but some people cannot do this, so two "tapped r" sounds can be used instead. The "y" can be tricky for some: It has the rounded lips of "oo" but the forward tongue of "ee", so put your tongue forward as if to say "ee" and (while keeping the tongue in that position) round your lips as if to say "oo"; it is same sound which is written as "ü" in German (click for voice file). And finally the "ch" is pronounced like a strong "h", to put it simply, like the German "Bach" (click for voice file).

Now, raudh is monosyllabic, so it is stressed by default. And in errych the stress falls on the initial syllable, like "ERrych". You can also use this IPA-reader website by copying the following text into the text-box and choosing "Dora [Icelandic]" or "Karl [Icelandic]" voices to read it for you (the others do not pronounce it correctly in this case), here:

ˈraʊð ˈɛr.ryx

That's beautiful, thank you so very much! Your ability with language is much appreciated.

A bit late, bit if you'd like the Quenya version as well, I'd say something like Entulessë Arroccoron, similarly meaning "Return [lit. "Coming-again"] of the Noble-horses."