This is the 3516th most frequent Korean word.
몇년
"몇년" means "how many years" in English.
Here, '몇년' asks about an elapsed duration from a specific event.
제가 태어난 지 몇년이 지났는지 몰라요.
I don't know how many years have passed since I was born.
Here, '몇년' is used to question or indicate an approximate duration of years.
몇년 동안 한국에서 살았어요.
I lived in Korea for several years.
In this example, '몇년' refers to an indefinite number of years in the future.