Normally, we can use 안녕하세요 (annyeong haseyo) in place of "Good morning/afternoon/evening" as a greeting. If you want to say good morning literally, 조은 아침 (joheun achim) or 좋은 아침입니다 (joheun achimimnida) are correct. But, I don't think Korean really use these phrases as greeting. I just hear 안녕하세요 in the whole time. Hahaha... As for 굿모닝 (gut-mo-ning), it's just Korean way to write the pronunciation of Good Morning.

joh eun achim ibnida

조은 아침 or 굿모닝 I guess one of these could be correct.

I'd like to know as well! maybe 좋은 아침입니다 but that's a guess not an answer.