Without knowing what questions you are referring to, first consider if we should be sending valid questions/users off to another site. 

[**Respect the community — your own, and others’**](https://blog.stackoverflow.com/2012/03/respect-the-community-your-own-and-others/)

But on a technical note, it is not possible to close a question as a duplicate of one on another site. Migration paths are not added until a site becomes a lot more established, so if a question truly belongs somewhere else, you can 'flag' it for Moderator attention. But even then, migrations are fraught with problems so we don't generally recommend them anymore. 

If the author simply asked a question on the wrong site, you can politely ask them to repost their questions in the context of the correct site. But posts sent off to another site the author did not intend means losing the reputation earned by all the authors on *this* site, and orphaned posts are greyed out as anonymous when the authors don't have an account on the target site. You also end up with comments that don't make sense and often the posts/voting may not fit the target site. So generally speaking, migrations do not work that well, so they are generally not recommended a routine way to shuffle questions off to another site.