BKARCUST contains customer information; however, not linked to your sales order.
BKARINV contains sales order header infomation, including the fields for bill-to and ship-to customer details.
BKARINVL contains sales order line item information, such as fields for part codes, prices, quantities, and the like. It is linked to BKARINV through the sales order number, meaning that you have to create the appropriate relationship between those fields in Access.
One note of caution... Access doesn't like DBA's use of fields ending with a number enclosed by brackets.
Good Luck!