It isn’t exactly the OS at a version/release that has it. It’s the iSeries Access product that has it. That’s perhaps a minor point, but it’s not clear what possible implications are in your question.
AFAIK, Client Access V3R2 (previous name of iSeries Access) was the first to have the Excel addon for file transfers. That would mean that all of version 4 and version 5 would have it as well.
If there is a more detailed question based in a problem you are having, please add comments to explain.