Hi togfish, and congrats on new tractor, I have had my 3560 for a year now and I love it.
Here is what it says in the shop manual, I have not had to do it so no firsthand experience.
First are you comfortable with the method Kubota uses to input or access computer settings on the Intellipanel? Short pushes of the display mode button to the left of the steering wheel "scroll" through choices, and long pushes select an item, and typically take you to another screen.
There is another method of bringing up another set of items. This I have not tried so am just typing in from WSM. You hold down the display mode switch and at the same time turn the key to start. I assume you do this when the tractor is not already running. You should then get a display called "service inspect".
It shows a bunch of letters, A, B, C, D, etc. Select J. This should show two choices and you could select mph.
What is not clear to me is how long you hold the key in the start position, and how you back out of this mode. It ought to be obvious from the display, but I wouldn't guarantee it. One caveat, the other letters go to setings that you do NOT want to mess with or change....
Hopefully someone who has done it will log on and chime in.
Or call your dealer on Monday