@@@ dual and plural forms representative of nouns in the same class
Qenya
illi
as many as
earendel
masculine name. Earendel
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 correlative ᴹQ. illi “as many as” appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of the relative pronoun ᴹQ. i and ᴹQ. -lli(ni) “many”.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. yallini “as many as” using the relative pronoun ya more commonly used in declined forms in later writings, such as Q. yassë “where [relative]”.