Relative Pronoun

Please dear teachers,



Can you help me with this?

Which of the sentences has the right use of relative pronouns? And why?



1. I know several cases when people have complained about the new restaurant.

2. I know several cases in which people have complained about the new restaurant.

3. I know several cases where people have complained about the new restaurant.



Which is the right relative pronoun?

And, is it defining or non-defining?



Thanks to you all.