Hey @VarshaAhir 

Unfortunately, I don’t think that’s a possibility at this point.

What I’m seeing is that we can convert a post to question/conversation/idea - but not a poll. Poll exists within a post so you would need to already include that within your post during creation time itself. I’m also not seeing an option to add a poll once the post has been published either. 

I see a similar idea about this created already here, if you’d like to vote in.