To connect ShipStation to Big Business you need to set up the Shipping Connect add-on (or let us do this for you) and in the ShipStation ODBC Client configure a Store to use Custom Queries starting with CountOrders.sql.
This Solution describes creating this file. (7083)
In ShipStation ODBC Client create a Store using the DSN you created and set it
SELECT count(*) FROM `SO` WHERE `ModMyTimeStamp` >= '{MinDateYear}-{MinDateMonth}-{MinDateDay}'
AND `ShipCtry` = 'US';