How can I see how many orders shipped for a specific date range?

Select ALL from underneath the Manage Shipments portion of the main menu. Here, you will be able to view the status of all orders. Select 'Shipped', which is the last status on the page. From the filter tool on the right hand side of your screen, scroll down to the 'Shipped Start Date' and 'Shipped End Date'. Enter the date range of your choice and click 'Apply Filter'.