To express that you have done something, use ~본 적(이) 있어요 :

유럽에 가본 적(이) 있어요 = I have been to Europe.

(유럽 = Europe. 에 = to. 가 = go. 본 적(이) 있어요 = have been)

The (이) is optional. In daily speech the 이 can be dropped.

~본 적(이) 있어요 can be used to ask whether you have tried something :

햄버거 먹어 본 적 있어요? = Have you [ever] tried a hamburger?

(햄버거 = hamburger. 먹 = eat. 어 본 적 있어요 = ever tried)

You can also ask whether you’ve tried something~어/아/해 보다 :

이 컴퓨터 게임 해 봤어요? = Have you tried this computer game? (Literally :  have you done this computer game)

(이  = this. 컴퓨터 = computer. 게임 = game.  해 = do. 봤어요 = tried.)

Let’s compare the differences between the two :

떡 먹어 봤어요?= Have you tried the rice cakes?

떡 먹어 본 적 있어요? = Have you [ever] tried rice cakes?

With the second sentence, the person is asking, “In your experience, have you ever, or at least once in your life tried a rice cake.” In other words the second sentence is asking you to recall whether you have ever, in your lifetime tried a rice cake, but the first sentence is simply asking whether you’ve tried the rice cakes.

When you want to express that you haven’t ever done something use ~본 적 없다 :

지갑을 잃어 본 적 없어요 = I have not lost a wallet [in my life]

(지갑 = wallet. 을 = object marker. 잃어 = lose. 본 적 없어요 = have not)

When you use ~본 적 없다, you’re basically stating that you’ve never done something in your entire lifetime up to now.