“فَ” (fa)a joining word meaning “then / so.” It connects this word to what came before.Corpus grammarCONJ — prefixed conjunction fa (then / so).
“َامَنُ” (āmanu)means “And they believed” in this verse. It is a verb. an action or state word. Here it is perfect verb, verb pattern four, third person — masculine — plural.Corpus grammarV — third person masculine plural perfect verb.
“وا” (wā)an attached pronoun meaning “they” or “them.”Corpus grammarPRON — third person masculine plural subject pronoun.