Facebook & Instagram tab, step 3: switch on Send leads and sales to Meta. ADs sends each lead and sale to your pixel through Meta's Conversions API every hour, with the Facebook click id when there is one, so Meta can match it to the ad.
Choose which to send: those traced to a Meta click, those credited to Meta by UTM tag, or everything (Meta matches the ones its ads influenced). Use Send test events with Meta's Test Event Code to see it arrive in Events Manager.
Event ids match a browser pixel that uses the order number, so nothing is counted twice.