How do you say You've got pretty eyes in Korean?

Koreans don't use you've got pretty eyes. 

If you really want to say the expression, then here you go. 

눈이 예뻐요 (Nuni Yaepuhyo)

But, Koreans don't use the expression to flirt 

If you want to flirt, don't say such thing.

Just say 

첫눈에 반했어요 Chunnunae bahnhatsuhyo

I fell in love at one sight

번호가 뭐에요? silraejiman bunhoga muhaeyo?
Excuse myself for asking this. What is your number?

But you gotta be brave enough and have "a good look" to get her/his number