Which reservation number for room request fax?

My room request fax will be sent out tomorrow, I think; suddenly I’m wondering which number I should put for the reservation number - the confirmation number that shows on MDE? or the longer number I was given by Orbitz when I booked with them (that I used to link the res in MDE)? I’ve done the fax several time before, but I can’t remember which number. Thanks!

You want the disney number on MDE