Export / import just a part of a website

Hi,

I've got a site where some contents (posts) are today totally off-topic. So I'd like to export them and everything that is related to them (posts, comments, media, anything else related) to import this stuff into a new site (actullay into a subsite in a multisite network).

I don't think Snapshot is capable of such a granularity (but maybe I'm wrong). So what solution would I have?

Thanks!
Best Regards