When you cast Mystic Confluence and choosing the 3rd option (draw a card) three times, how many event(s) are occurred?

My thought:
If it is one, then the card will say draw three cards and it can be replaced by Alms Collector replacement effect.
If it is three, then logically it can't be replaced by Alms Collector replacement effect because you are not drawing three cards but one card three times.

If someone can explain it to me more detail, please do so.

As Mystic Confluence resolves, it instructs you to draw one card, then it instructs you to draw one card, then it instructs you to draw one card. Since Mystic Confluence is never instructing you to draw multiple cards using a single ‘draw’ verb, Alms Collector's ability will not apply, since the Collector only applies to effects that instruct you to draw multiple cards.