If you look in the spec pages of your Clymers book you will find you front rim is 1.85 inches wide. Take the inches and multiply by 25.4, thats how many mm's there are in an inch. So 1.85 X 25.4 = 46.99 mm for the rim width.
The 3.50 tire is 3.50 x 25.4 = 88.9. So a 90/90-19 would match the spec tire closest. problem is not too many tire companies makes one.
Most run the 100/90-19 or the 110/90-19. either tire will work fine. I like the 100/90-19. A bit quicker turn in.
The rear rim is a 3.00 inch wide or 76.2 mm wide. With a 130/90-16 tire. For a better handling bike, get an 18 inch rear wheel and run a 120/90-18. The skinnier tires will turn in quicker.