Hi,
the message means that in the new object that you are trying to import the definition of the field Sales Order in the table Customer 18 is changed.
My suggestion is create a new custom field in the table Customer 18 like "Sales Order Copy" with numeration > 50000, then create a report for service to move the values from the Sales Order field to the new field for all the companies.
Then after you will be sure to have a copy of all the original values run a new report for service to delete for all the companies the values in the field Sales Order.
In this manner you will can import the objects and after importation you can understand if in the new version they changed the type of the original field or removed.
To know HOW TO CHANGE DATA FOR ALL COMPANIES read my following post
www.myerrorsandmysolutions.com/how-to-change-data-for-all-companies
I would solve the problem so