In internet explorer, you can click on tools "View source code" and it will show you all the HTML for the page. Then it should say Google Adsense and a publisher number in a snippet of code where the ads are placed in the html.
There is a 'placement tool' in the 'Networks' tab of your ad groups. Click the 'add placements' button to view it. This will allow you to search for whether a specific URL uses AdSense, or all sites of a category, etc.