Both Smashwords and Amazon let you see how many copies your books have sold. The numbers are updated every few hours.
Here's how to find the numbers. The two sites are not very accessible, unfortunately.
Go to https://www.smashwords.com/ and log in.
This takes you to the Smashwords home page.
You'll see blue bar across the top of the page with links showing in white letters. Click on the link labeled Dashboard.
This takes you to the Dashboard page. On the left of this page are some links that show you sales and payments. They all have interesting information, but the simplest one is the one labeled Daily Sales.
Click on that link and you'll see a graph showing your sales for the last 30 days. There are buttons across the top that let you select a different period of time. There are also buttons for other display options.
Go to https://kdp.amazon.com/ and log in.
This takes you to your Bookshelf page. Across the top of the page are links in blue letters. Click on the one labeled Reports.
This takes you to a graph displaying your sales for the last 30 days. There are buttons that let you change what's displayed. For example, you can change how far back in time the display goes.
There are also links in blue lettering higher up on the page that show other kinds of information, including the payments that have been made to you. The link you might find interesting is labeled Month-to-Date. If you click on that, you'll get a tabular list of sales so far in the current month. By default, it shows only e-book sales, but there's a button you can use to change to paperback sales. Also, there's a button that lets you switch to all the sales for the previous month.