a fish out of water
This idiom is used to describe someone who is uncomfortable in a certain situation. There is a Turkish idiom used in the same way.
Imagine that you are still in the highschool and because of your parent s’ job you have moved to another city in your last year. It was quite comfortable for you since you had spent 3 years in the school and you have had lots of friends there. However, you have found yourself in an unfamiliar place all of sudden. When you call friends of yours in the previous school, you might say: “I feel like I am a fish out water. I have no friends here.”
P.S By the way, your friend should say: “Don’t worry. You will make friends there, too.”