If we say the goal of the user is to quickly find the best product when browsing the product listing page. What are the pros and cons of providing users the option to sort by Number of Reviews? Does sort by Number of Reviews support the goal?
I think it really depends on the user. Some users will value the ability to sort by number of reviews, and some will be happy to just see the review score.
Basically, "number of reviews" is useful because it allows the user to determine how reliable the rating is. For example, assuming your rating system shows an average score out of 10 stars, "9 stars from 1,000 people" is a lot more reliable than "10 stars from 1 person".
To that end, it might not be that you need to be able to sort by number of reviews, but showing the numbers of reviews alongside the average rating is very useful.
So yes, I would say sorting by number of reviews will support the goal of some users.
I would also say there isn't really a downside to providing the ability because nobody is forced to use it if they don't want to. The only possible drawback might be if the design is cluttered by the addition of that sorting option, but that would be down to you to solve.