Hey, I wrote a guide to this on my website.
That being said, if you use the Marketing Cloud Visitor ID (Adobe Analytics ID) as the value for the `transactionID` column, your upload will work as expected. And you don't need to set anything for `s.visitorID`. This will be populated automatically by the `mcvisid` if `s.visitorID` isn't specified.
You can obtain this value from the `mcvisid` column in an Adobe Data Feed.