I need help with serial communication between Arduino Uno and NodeMCU

Question

I want to transfer analog readings i.e. variable values from a NodeMCU to an Arduino Uno so that on the Arduino side I can check those values using an if condition and make a buzzer sound. Please help with the connections of the RX and TX pin wires and also with the code.

NODEMCU CODE:

int mq6 = A0; 
int d = 0;
 
void setup() {
  Serial.begin(9600);
  Serial1.begin(9600);   
  pinMode(mq6, INPUT);
  Blynk.begin(auth, ssid, pass, "blynk.cloud", 80);
}
     
void loop() {
  Blynk.run();
  d = analogRead(mq6);
  Serial.println();
  Serial.print(d);
  Blynk.virtualWrite(V0, d);
  Serial1.println(String(d));

  if (d > 500) {
    Blynk.logEvent("warning_leakage", "Temp above 30 degree");
  }      
}

ARDUINO CODE:

void setup() {
  // Serial Begin at 9600 Baud 
  Serial.begin(9600);
  Serial1.begin(9600);
}
    
void loop() {
  int d = Serial1.parseInt();
  Serial.println(d);
  delay(100);
}