I know you are trying to do this your self so i will throw some spaghetti at the wall and see if it sticks.
LEGAL DISCLAIMER: YOU PROBABLY NEED A REAL PLUMBER.
Duct Tape a piece of cardboard over the hole in the floor ( larger than the opening ) and then place a template ( or the pan for that mater ) on top of that then mark the hole location with a sharpie on lower paper and then cut that hole out of the cardboard. Remove the template/pan, you now have the piece of cardboard over the hole with a hole in it that is were the drain should be. Leave one side of the cardboard taped so you can hinge it in and out of place.
You may be able to use a short turn 90 degree elbow coming of the shower drain bell to a short peace of pipe and the either a street 90 or short 90/pipe into the P trap. The Template will help with lining it all up if you know the height or the shower pan drain bell. Get a bunch of fittings and pipe to cut into short pieces and play around with it. Its going to take a lot of thinking and trial and error. Maybe it is something compleatly different like 45 degree fittings and ???
NOW having said all that , you will not be able to make any connections ( I.E. glue any fittings ) after the pan in place and that means you need exact precision and placement of the fittings so that when the pan is put down into place the bell lines up and the plumbing is at the correct height. That means dry fitting EVERYTHING and putting the pan in place and checking it.
REMEMBER: distance or measured pipe length's change from dry fitting to wet gluing. DON'T SHORT YOURSELF
I do not know anything about your pan or bell and what height it will be, and even if i was there it would tax my brain to figure it out.. ( I CHARGE BY THE HOUR )
Good luck and remember you did not pay for this "advise" If it works i am a genius and if not it is your fault. :)