Use amount with uncountable nouns – things that cannot be separated or counted.
▶️ There’s a significant amount of traffic in the late afternoon.
▶️ She inherited a large amount of money from her grandfather.
▶️ This recipe requires a small amount of wine.
▶️ I have a huge amount of work to do this week.
Use number with countable nouns – words that can be counted and made plural:
▶️ A number of my friends are teachers.
▶️ A large number of people complained about the restaurant’s terrible service.
▶️ This recipe has a small number of ingredients.
▶️ I have a huge number of tasks to do this week.
The word quantity is a more technical/formal word for number or amount, and it
is used for things you can measure (usually objects, not people).
▶️ We have a limited quantity of special-edition hats for sale.
(or: a limited number of special-edition hats)
hats = countable
▶️ They need a large quantity of cement for the construction.
(or: a large amount of cement)
cement = uncountable