99% chance the belts are broken or melted. The cassette player mechanism is held into the main body by four screws, you need to remove the front face (another four screws) to get to one of them. They're 1/4" hex screws. Once you get the cassette player free of the chassis, turn it over and carefully remove the ribbon cable for the front buttons by releasing the connector and pulling it out. Under that, there are three Philips screws holding on the bottom cover, remove those and hinge the cover off. The motor pulley and two capstan pulleys are accessible, as is the drive belt if it's still there. Don't turn the deck right-side-up with this cover off, the two large pulleys are not held in and will fall out. I can't tell you where to get replacement belts, but replacing them will probably fix your problem with them... At least mechanically.
The reason you're only hearing clicks is because these decks have little solenoids that engage gearing driven by the capstan pulleys. No belt, nothing moves.