To see only paid ads on your Facebook news feed you will need to install the extension of your web browser (currently only works with Google Chrome).
Extensions are Turbo Ad Finder or Bigbigads. You can install both extensions on Chrome through the following link https://chrome.google.com/webstore/category/extensions or in the Chrome menu, select More Tools> Extensions, and in the bottom section, click Get more extensions.
By installing these extensions, you will be able to activate and deactivate them on the Chrome menu in the top right corner. When you’re on your Facebook page in Chrome, you can only see paid ads by activating the extension. DO NOT FORGET to deactivate the extension when you are finished to view all posts.
TIP: With Bigbigads you will also be able to see some additional statistics like targeting, frequency, and so on. even in the Free version.