Power gear hydraulics use a spring to "Suck it up" as it were.
I see no way the jack can "Self Extend" though air in the lines can do strange things. but that would take a lot of air.
IF, the jacks are hydraulic..
You need to park with the rear wheels HIGHER than the ground, This can be very tricky but there are many places you can do it or you can build a set of "Stair Step" ramps such as I use to get the wheels off the ground, I do not know how much but I'd guess at least six inches
Extend jacks all the way (use the manual override to extend the rear jacks, both of them)
Book says 3 times should do it but I would go 4
And that's it.
You might wish to ramp up the front tires and do it with them too.
My plan (I need to replace a pretzel, used to be a jack) is to put brake bleeder valves in the plugged port and use them instead of tricky parking.
Home is where I park it!