V+(으)ㄴ 지 N 됐어요 is used to express how much time has elapsed between when an action (V) occurred to the present point in time.
한국에 온 지 얼마나 됐어요?
How long has it been since you came to Korea?
운동을 시작한 지 일주일쯤 됐어요
Its been about a week since I started exercising
서을에 온 지 일 년 됐어요
It’s been a year since I came to Seoul