Three syllables: Nær-øy-fjord. (Literally Near-island-fiord.) Æ is the same sound as in (English) bad; øy is is a diphthong starting with a sound much like the vowel in rough and ending with a sound much like the e in me. The o in fjord is a sound somewhere between those in Rome and room.
I think there used to be a web site where you could type Norwegian text and hear it being pronounced, but I can't find it now.
Here is an online text-to-speech generator for Norwegian. Be sure to type in Nærøyfjord using the Norwegian letters. Press "Read" to hear the pronunciation.