Trying to find information on ther serial spec was not easy but it is 4800,8N1 with no flow control.
Try a slightly different sketch an see if it works. You will need to alter the serial monitor baud rate to 4800
void setup(){
Serial.begin(4800);
Serial3.begin(4800);
delay(1000);
Serial.println("Setup Complete.");
}
void loop(){
while (Serial3.available()){
Serial.write(Serial3.read());
delay(1);
}
while (Serial.available()){
Serial3.write(Serial.read());
delay(1);
}
}