You can view the paid traffic data for a website via Site Explorer's Paid Search tab. This report shows you the Top Ads, Top 5 paid keywords and Top 5 landing pages:

If you want a more detailed report, you can go to the "Paid Search" section on the sidebar, where you can choose to view the Paid keywords, Ads or Paid Pages used by the site you're analyzing:

Here are some definitions of the terms we use: 

Paid keywords are keywords you bid for inside Google Ads. You pay Google a fee for each click in order to appear in their sponsored action for keywords related to your business. 

Inside the Paid Search report, Ahrefs shows the keywords the target site has bidded for. 

Note: Sometimes you may find that a keyword your competitor is bidding is not shown in the "Paid keywords" report. Read this article to find out why. 

Paid traffic value shows the estimated monthly cost of paid search traffic from all the keywords a target website/URL ranks for via pay-per-click (PPC). 

The Traffic metric under the Paid Keywords section, refers to the percentage of paid traffic generated to a target website/URL by a given keyword. 

Please note that these percentages are only an estimation based on the last known paid positions on the target site. 

Learn more about traffic value metric here.