How to say it? (japanese)?

Question:

Hi ^^ I want to ask You how to say: "Thank You for these 3 years" in japanese :3 It's very important to me and I want to tell it to very important to me person.

And please,answer if you really know japanese,without google translate or something like that~

Answer:

この３年間、本当にありがとうございました。
kono san nenkan, hontouni arigatou gozaimasita.