Hi there @oldtimer - I don't have much experience with DOS, so can't offer a lot of help on that side. However, if you find a way to export your customer and product information from DOS to a CSV or Excel file, you'd be able to import it via your Square dashboard.
More info here on importing your customer information to Square: https://squareup.com/help/us/en/article/5498-manage-your-customer-directory-online
And here are some more details on importing product information to Square: https://squareup.com/help/us/en/article/5153-import-items-online
Hope this helps! I'll keep an eye on this thread - now I'm curious too about whether the DOS export can be done!
