Log in to your bookingkit account and head to Orders export under Statistics -> Export.
If you select Payment date field, this will be one of the column in your export file. Orders that have not been paid yet are marked as "On-site payment".
Select the period you would like to generate the export for. Only bookings that were made in this period will be included in the file. You can also choose what format the file should be exported in. You can choose between .pdf, .excel and .csv.
Learn how to split text into different columns using the Convert Text to Columns Wizard in Excel here.