"Are there three?"
It should be fine. However (just in case anybody else besides me needs to remember what "-ne" means):
Particle -ne (interrogative enclitic)
Added to the end of a word in a phrase (usually the first word) to make it a question. -- Nihilne in mentem? (Does nothing suggest itself to your mind?) -- Ah, pergisne? (Ah, at it again?) -- Esne iratus, frater? (Are you angry, brother?) -- Potesne mihi succurrere, quaeso? (Can you help me, please?)
or… (introduces a question or an alternative)
- A question requiring an answer of "yes" or "no" is formed by adding -ne to the emphatic word: -- Is tibi mortemne vidētur aut dolōrem timēre? (Does it seem to you to be death that he fears or pain?) --Hīcine vir usquam nisi in patriā moriētur? (Shall this man die anywhere but in his native land?) -- Tūne id veritus es? (Did you fear that?)
*The enclitic -ne is sometimes omitted.
Patēre tua cōnsilia nōn sentīs? (Do you not see that your schemes are manifest?)
- When -ne is added to a negative word (such as nōnne) an affirmative answer is expected. -- Nōnne animadvertis? (Aren't you paying attention?)
[Taken from Wiktionary: https://en.wiktionary.org/wiki/-ne]