Depending on where you paid for the domestic flight booking, you may check the Order Number as below.
If you purchased the ticket on JAL website, you may find the Order Number on the "Purchase Complete" Page.
A sample of e-Ticket itinerary/receipt issued at designated travel agency
A sample of e-Ticket itinerary/receipt issued at JAL Group domestic ticket counters at airports
A sample of receipt/customer copy issued for cash payment at convenience store in Japan
(Image is a sample issued at Lawson.)