You have a few ways to do this.
One would be to search for competitor ads on the same niche. When you are browsing the ad info, you will find a section called “Videos where this ad was found”. If you find a video where the ad was shown multiple times, chances are, this video is profitable.
Another way would be to go to these 2 reports:
In both of them you can narrow down by niche and timeframe to get more accurate results.
Finally, you can use the section called “Find Ad Placements“, where you can search for videos, channels and keywords and create your own lists.
For example, if you go to “Videos” and enter a term like “Weight Loss”, you will find several relevant videos. From that list, you can see video info like views, likes, etc., and any ads that were shown on that particular video. You can then add one or more videos to a placement list, and use that list for your ads.
You can do the same with channels and keywords.