Early Quenya
yunqenya
ordinal. twelfth
yunqetya
ordinal. twelfth
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
The word for “twelfth” in the Early Qenya Grammar (EQG) of the 1920s was ᴱQ. yunqetya (manuscript) or yunqenya (typescript), both based on ᴱQ. yunqe “twelve” (PE14/51, 82).
Neo-Quenya: For purposes of Neo-Quenya, I would update this word to ᴺQ. yunquëa “twelfth” following later patterns for ordinal numbers. Compare Q. neldëa “third”.