Correção de frase: If someone told me, I wouldn't believe.

Hello. A little help, please. I don't know how to construct a sentence.

Let's imagine a situation: I won a prize that was an airplane ticket to visit Japan. So I went there and, during a small-talk with a friend, I said:

If someone, last week, (had) told me that today I would be in Japan, I wouldn't believe.

Is this sentence correct? I find strange use "told" in this hypothetical situation with the "if".

I also put "(had)" because I don't know if It's good to use it. And this "last week" is being a puzzle to me. I don't know where to fit it.

Is Spanish is (creo) "Si, alguien, semana pasada, me dijera que hoy yo estaría en Japón, yo no lo creería."

In Portuguese is "Se alguém, na semana passada, tivesse me dito que hoje eu estaria no Japão, eu não acreditaria.

All kinds of help are welcome.
Thank you ever so much.