On a 1999 Hyundai Elantra sedan, the windshield washer motor is typically located
behind the front bumper, near the passenger side. You'll likely need to remove or partially remove the bumper to access it. It's often attached to the washer reservoir.
However, accessing it requires some disassembly, so consulting a repair manual specific to your 1999 Elantra model year is highly recommended. A repair manual will give you precise location diagrams and instructions to avoid damage.