Bootloader errors help for newbie

I'm completely new at this and have no idea what i'm doing and need help! I've tried every COM available and none of them are working. This is the code I have:

//This is the script to collect data on muscle contractions using the Myoware sensor.

const int analogInPin = A0; // Analog input pin that the muscle sensor is attached to
int sensorValue = 0; // Variable to store the value coming from the sensor
int outputValue = 0; // Variable to store the adjusted sensorValue

void setup() {
// initialize serial communications at 9600 bits per second:

// The loop routine runs over and over again until you remove power
void loop() {
sensorValue = analogRead(analogInPin); // Redefines sensorValue variable based on current measurement
outputValue = map(sensorValue, 0, 1023, 0, 255);
unsigned long currentTime = millis(); // Defines variable based on how long the sketch has been running (in milliseconds)
// Serial.print(currentTime);
// Serial.print("\t");

This is one of the errors I received:

avrdude: error: programmer did not respond to command: exit bootloader
avrdude: error: programmer did not respond to command: exit bootloader

I've followed every instruction given to me to a T and the code is what my professor told us to use. Any help would be greatly appreciated!

Please do this:

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