Since movies SE have decided to ban id question and delete all the existing ones, I'm asking if it's possible to save part of its archive (scifi related questions) by migrating them here? And if it's possible how to do so (I'm not familiar with how migrating works)?
Yes, this should definitely be done.
When the old Literature SE was shut down (not to be confused with the new one), all of its sci-fi and fantasy questions were migrated here, so that the content could be kept in a place where it's wanted rather than irrecoverably lost. (This even included some ID questions.)
The current situation is similar, except that it's not an entire site being shut down but only around 1/3 of one (by question count). Any questions which would otherwise be deleted on M&TV, and which would be welcome here, should certainly be migrated. That's the way migration works: if a question is off-topic on the site where it's posted, but would be both on-topic and good quality on another site, then there's no reason not to shunt it over.
Note that this doesn't necessarily cover ALL sci-fi and fantasy ID questions on M&TV. That site gets a lot of very low-quality ID questions, and some of them would doubtless be too crappy for us as well. Let's not go overboard here.
As for how to nominate a question for migration (which you mentioned in comments), the answer is simple: just flag it for mod attention over there. It's the M&TV mods who need to migrate these questions. But they have no reason not to do so if they know a question would be welcomed here (e.g. if it was flagged by someone who knows SFF's scope well), so there shouldn't be any disagreement.
As a CM said in a related meta post on another site about migrating ID questions to SFF:
if anyone who is really active at SF&F and familiar with their guidelines sees something here they definitely think is a good fit there, great! Flag it!
I've already opened a meta post on M&TV about this too.