In Ecuador, the official currency and the only currency used is the US dollar.
When you arrive in Ecuador you must buy dollars. For doing that, you have to go to a exchange house. Avoid buying dollars on the street, look for ?reliable exchange houses.
Depending on the country you come from, your money will have a specific value.
Here you can find out how many dollars you can buy with the money you have available: https://www.xe.com/
Remember! The exchange rates given by the website are referential and may change from day to day.