I'm afraid this is not really a use case that was envisioned and that Codidact has no support for this. But actually the problem in doing this at all is that SO for teams (to my knowledge) does not offer any import functionality. We are no longer using it at the university where I work, so I can't double check, but I don't recall seeing such an option.
Note that the other way around, SO to Codidact is possible (we've done it a year ago). I wouldn't call it easy to do, and the process could be improved, but it is possible at least.