I don't have iPhone but want to register AirPods to find me using my mac

pretty sure you can't

you need to understand how find me works for airpods

airpods does not have gps

airpods only means of communication is bluetooth so about a 50meters range

the way find

my works in terms of airpods is that the iphone use it's own position last time it had contact with the airpods

your mac also does not have gps but it can get around that by getting a location from the router it's connected to