not specific advice here but generalizations. Usually when someone has done a sport and taken time off it comes back fairly quickly. Of course age, skill, skill level you were at before leaving are all factors.
So since your did not say let assume you were a solid rider before your 3 year break. I would bet after the first day of getting used to it agian, your skill will start to kick in. After day 2 you will probably be pretty comfortable on the board.
After day 3 you'll be done, your body will be so sore from riding you will probably need a day break.
Hope you enjoy the trip and the skill should come back to a level that you will enjoy your self a lot. Maybe not park but general mountain riding