If your client's accounting software has the option to export transactions in an MYE format, choose this option. This is an MYOB file type and requires no additional formatting.
If you don't have this option, choose a .CSV or Excel file type. These files may require some additional customisation to import into MYOB ledger.
If you're not sure how to export data from a 3rd party accounting software, check the product help for that software.