How to control multiple LEDs with 74HC595 shift register using millis()

Hi, I'm new to using shift registers, trying to turn on and off some LEDs for a set duration, basically ' / if (____== HIGH) check if LED is ON / ' what do I fill in for this portion of code?

// put your main code here, to run repeatedly:
//the pins we are using
int clearPin = 5;
int latchPin = 6;
int clockPin = 7;
int dataPin = 8;

const unsigned long onDuration_0 = 1000;
unsigned long previousTime_0 = 0;
const unsigned long offDuration_0 = 3000;

const unsigned long onDuration_1 = 2000;
unsigned long previousTime_1 = 0;
const unsigned long offDuration_1 = 5000;

const unsigned long onDuration_2 = 3000;
unsigned long previousTime_2 = 0;
const unsigned long offDuration_2 = 1000;



byte register1 = 0;
 
void setup() { //runs once at startup
  //set all the pins used to talk to the chip
  //as output pins so we can write to them
  pinMode(clearPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);

  digitalWrite(clearPin, LOW); //Pin is active-low, clears shift register
  digitalWrite(clearPin, HIGH); //Clear pin is inactive / take the latchPin low so the LEDs don't change while we are writing data
  
}

  
  void loop(){
    /*Updates frequently*/
    unsigned long currentTime = millis();

  /* if (____== HIGH) check if LED is ON */
  if (currentTime - previousTime_0 >= onDuration_0) {

      for (int x = 0; x < 8; x++) {    //THIS SELECTS PORT 0-7 ON YOUR SHIFT REGISTER
      bitWrite(register1,0,LOW); // PUT LED 0 ON, shift register 1
      digitalWrite(latchPin, LOW);
      shiftOut(dataPin, clockPin, MSBFIRST, register1);
      digitalWrite(latchPin, HIGH);}    

 /*Update timer for next event*/
 previousTime_0 = currentTime;

  }
 /*else { */
  if (currentTime - previousTime_0 >= offDuration_0) {

      for (int x = 0; x < 8; x++) {    //THIS SELECTS PORT 0-7 ON YOUR SHIFT REGISTER
      bitWrite(register1,0,HIGH); // PUT LED 0 ON, shift register 1
      digitalWrite(latchPin, LOW);
      shiftOut(dataPin, clockPin, MSBFIRST, register1);
      digitalWrite(latchPin, HIGH);}    

 /*Update timer for next event*/
 previousTime_0 = currentTime;

  }


  /* if (____== HIGH) */
  if (currentTime - previousTimeOn_1 >= onDuration_1) {

      for (int x = 0; x < 8; x++) {    //THIS SELECTS PORT 0-7 ON YOUR SHIFT REGISTER
      bitWrite(register1,1,LOW); // PUT LED 0 ON, shift register 1
      digitalWrite(latchPin, LOW);
      shiftOut(dataPin, clockPin, MSBFIRST, register1);
      digitalWrite(latchPin, HIGH);}    

 /*Update timer for next event*/
 previousTime_1 = currentTime;

  }
 /*else { */
  if (currentTime - previousTime_0 >= offDuration_1) {

      for (int x = 0; x < 8; x++) {    //THIS SELECTS PORT 0-7 ON YOUR SHIFT REGISTER
      bitWrite(register1,1,HIGH); // PUT LED 0 ON, shift register 1
      digitalWrite(latchPin, LOW);
      shiftOut(dataPin, clockPin, MSBFIRST, register1);
      digitalWrite(latchPin, HIGH);}    

 /*Update timer for next event*/
 previousTime_1 = currentTime;

  }

       
                                                      }

Your post was MOVED to its current location as it is not an introductory tutorial

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Think I found my answer on my own, possibly its' if (bitRead(register1,1)== HIGH) '