~ㄴ/는/다면, (이)라면 (eun/neun/da-myeon, (i)-ra-myeon) – if (this/that happens), then…
Essentially, ~ㄴ/는/다면, (이)라면 is more or less the same thing as ~면 just that you would usually use ~ㄴ/는/다면, (이)라면 if the hypothetical situation you’re trying to express is something that is very improbable or very unimaginable.
You would attach ~ㄴ/는다면 to verbs, ~다면 to a descriptive verb/adjective, and ~(이)라면 to nouns.
Examples: 10년 전 돌아간다면 더 열심히 공부하고 싶어.
If I were to go back to 10 years ago, I want to study even harder.
누구가 이 기적의 약을 먹는다면 죽은 사람도 다시 살 수 있어.
If anyone were to eat this miracle pill, even a dead person can live again.
나 독수리처럼 어디든 날 수 있다면 셰계여행을 가고 싶어.
If I could fly anywhere like an eagle, I want to go on world trip.
나 부자라면 자선단체에 많이 기부하고 고아원도 짓고 싶어.
If I were to be a wealthy man, I want to donate a lot of money to charity and even build an orphanage.