Sage BusinessWorks does not have a way to merge parts.  You would need to delete the parts if they have no on hand quantity and no transactions on file for that part.

Please note that you can only delete a part as long as there is no activity for the months to keep history. You will need to use a negative adjustments to zero out on hand quantity for the part you no longer want to use, and then a positive adjustment for the part you are keeping. Then you can rename the obsolete parts to a letter or number to send them to the bottom of your part list so that you can select to run reports excluding those parts until you reach the months to keep history and can delete them.

Please note that you can only delete a part as long as there is no activity for the months to keep history. You will need to use a negative adjustments to zero out on hand quantity for the part you no longer want to use, and then a positive adjustment for the part you are keeping. Then you can rename the obsolete parts to a letter or number to send them to the bottom of your part list so that you can select to run reports excluding those parts until you reach the months to keep history and can delete them.