There isn’t currently a way in the UI (though plenty of requests for it if you want to add your voice/vote Add the option to change a topic to Post Voting format by admin/staff)
I believe it is possible using the rails console...
I think you need to change the topics.subtype to ‘question_answer’, though I haven’t given it a runthrough recently to double check if that’s all that’s needed, so you may need to test first.
Possibly also changing all the posts types so they’re not considered ‘replies’ may also be part of it. Post Voting topics don’t like ‘replies’ so that may necessary too.