"What is her phone number?"
The answer is 彼女の電話番号は何ですか in Kanji. It looks quite similar to me. So I'd treat them as the same one.
Can someone explain why the の and は are where they are? Just need clarification
の no - is a particle that denotes possession. は ha (voiced wa) - is a particle that indicates the topic of the sentence.
かのじょの電話ばんごうは何ですか kanojo no denwa bangou wa nani desu ka
かのじょの電話ばんごう, that means “her phone number” is the topic of the sentence and that's why は goes after it.
I a bit confused as to whether the 'nani' needs to be in the front of the sentance or near the rear?
Not a native speaker, but I think usually the subject or object of the sentence should be established first (in this case, the girl's phone number), before taking an action on it (such as asking for it).
The transliteration of the Japanese sentence would be something like, "As for her phone number, what is it?" It doesn't flow too well in English (hence the official answer is "What is her phone number?"), but that's one of the idiosyncrasies of the language I reckon.