trouble with HC-SR04 and 5V DC motor

Projects Programming
3

this is my code at the moment

const int trigPin = 2;
const int echoPin = 4;
int motorPin = 3;

void setup() {
// initialize serial communication:
Serial.begin(9600);
}

void loop()
{

long duration, inches, cm;

pinMode(trigPin, OUTPUT);
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

pinMode(echoPin, INPUT);
duration = pulseIn(echoPin, HIGH);

inches = microsecondsToInches(duration);
cm = microsecondsToCentimeters(duration);

Serial.print(inches);
Serial.print("in, ");
Serial.print(cm);
Serial.print("cm");
Serial.println();

delay(100);
if (Serial.print > 20cm) {
digitalWrite(pinMode, HIGH);
} else {
digitalWrite(pinMode, LOW);
}
}

long microsecondsToInches(long microseconds)
{
return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds)
{

return microseconds / 29 / 2;
}