Unfortunately, at this moment, there is no option to move questions from Confluence Questions from one space to another in Confluence Cloud. We do have an open feature request to implement this option in the future releases/updates, which you can check in the link below:
Please check this feature and vote for it if you want to see it implemented.
Confluence Questions in Confluence Cloud is, unfortunately, just a mess. There's no way to prevent questions from winding up in a space where they won't be seen (admin needs control over this), no way to ensure that users will see notifications (admin can't set it, users aren't reliable to set it, "watch all" construct is odd/confusing, no way to see who is and isn't following), and even when users do "watch all" to see notifications sometimes they are never sent (and no logs to see what happened - an issue with Confluence notifications in general, not just Questions).
Continued references to old feature requests aren't much help. Confluence Questions needs some attention!
The option is still available (tested on the latest version of Confluence Questions plugin - 2.5.5). But to use it, you'd then need to first edit the question itself.
(i) You will only be able to edit the question if you have the Space Admin permission to the Space where that question is located. The options for edit & delete will appear below the textbox of the question
Hope this helps :)