so how I dont use pin 3 as an interrupt?
Simple: Delete this line:
attachInterrupt(RIGHT, RwheelSpeed, CHANGE); //init the interrupt mode for the digital pin 3
If you mean how can you use another pin as the external interrupt pin, you'd need to rewire the ATMega328 chip internally. I'm not capable of doing that, and I have my doubts about you.
You could use a Mega, which has more external interrupt pins, and different pins.
Are there really 4 independent motors on your robot?