Question

If had found that box , i would have returend it . ( change into type 2 sentance)

Answer 1

Answer:

Correct: If I had known that you were going to the movies, [then] I would have gone too.

The conditional perfect can only go in the “then” clause — it is grammatically incorrect to use the conditional perfect in the “if” clause:

Incorrect: If I would have known that you were going to the movies, I would have gone too.

More examples:

Correct: If I had gotten paid, we could have traveled together.

Correct: Had I gotten paid, we could have traveled together.

Incorrect: If I would have gotten paid, we could have traveled together.

Correct: If you had asked me, I could have helped you.

Correct: Had you asked me, I could have helped you.