http://sn-zw.facebookwkhpilnemxj7asaniu7vnjjbiltxjqhye3mhbshg7kx5tfyd.onion/business/help/835561738423867
When you select Flexible as your ad format, you can select up to 10 images and videos in a single ad campaign, and the ad delivery system will automatically determine what media or media combination, such as single image, video or carousel, to show to people.