The Discount Ninja dashboard provides an overview of the performance over the last few days for each of your promotions.
It lists the number of views, number of times activated (accepted) and conversions for each.
To get a detailed report of the performance per discount code go to Analytics > Reports in the Shopify Admin.
Note: not all reports are available to each Shopify subscription level. Find more information here: https://help.shopify.com/manual/reports-and-analytics/shopify-reports
Find the Sales > Sales by discount code report to get an overview of sales per discount code (i.e. affiliate).
Note: it can take up to 24 hours for the report to refresh.