Les éléphantes or les éléphants?
A female elephant is "une éléphante." A group of female elephants is "les éléphantes." A group of female and male elephants is "les éléphants" because mixed gender groups take the male spelling by default.
The L with the apostrophe is used when the word starts with a vowel, like a, e, i, o, u, or sometimes h or y, so you are technically correct. However, L' is overruled when the word is plural. Then, you always use les.