Since 1st Tracking
Email quick filter
Filter by source where 'affiliate' is in the string, which you will have if the customer is using the proper naming conventions for affiliate emails.
Otherwise, find the affiliate prefixed emails in the content filter.
Failing either of those 2 adopted naming conventions, find the emails based on whatever you know about your campaigns and affiliate marketing.
Even though you are looking at sales, I like to look at the campaign in order of how the emails were sent.
Look at the sales column to see if sales are occurring. Check for emails that should be closing sales, such as the last email of a campaign, and see if there is still click interest, and sales that convert higher than other emails in the campaign.
Keep the emails that are converting the best and use them for future affiliate email sends.