I am pretty sure of this: the files BKARHINV and BKARBINVL are the INVOICED Sales Order files, Header and Line items respectively.  The files without the H are the Sales Order files (BKARINV adn BKARINVL) A Sales order with no invoice towards it will only be in BKARINV and BKARINVL.  Once it is invoiced it is in both until purging takes it out of the BKARINV and BKARINVL files.  
 
I don't think you can currently archive Sales Orders.  You can Delete and Purge them.  I don't think you want to delete and purge your invoice history- I am not even sure that you can.
 
IN excel, using a query, you can choose the columns to list and set parameters for which records to bring in, such as only after a certain date, or in a date range, etc.
 
Hope this helps.