"한국에서 일한 적이 있습니까?"
Translation:Have you worked in Korea?
I've realised that it means past participle used to form the present perfect Like: I have done, you have been, he has worked, we have seen
(은/ㄴ) 적이 있다/없다 is a form you can add on to the end that adds the meaning "to have ever or have never done something." Usually you would see 아/어 본 적이 있다/없다. Which is "have you ever/never tried to do something."
"적이" also translates as "ever". Thus, the question ican be transpated into english as "Have you ever worked in Korea?"