Storing RFID UID's to output in serial monitor when a switch is pressed

Question

I am trying to store 4 UID's to be printed once a switch is turned on, the only way that I see to do this is with array's. But I am still pretty new to this language and I am pretty lost on how to go about it. Any help would be much appreciated, please feel free to ask Questions if you have any and I shall do my best to answer them

This is what I have for my code so far

#include <SPI.h>
#include <MFRC522.h>
#define SS_PIN 10
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance.

void setup() 
{
  pinMode(4,OUTPUT);
  pinMode(3,OUTPUT);
  Serial.begin(9600);   // Initiate a serial communication
  SPI.begin();      // Initiate  SPI bus
  mfrc522.PCD_Init();   // Initiate MFRC522
  Serial.println("Approximate your card to the reader...");
  Serial.println();
}
void loop() {
 
  // Look for new cards
  if ( ! mfrc522.PICC_IsNewCardPresent()) 
  {
    return;
  }
  // Select one of the cards
  if ( ! mfrc522.PICC_ReadCardSerial()) 
  {
    return;
  }
  //Show UID on serial monitor
  Serial.print("UID tag :");
  String content= "";
  byte letter;
  for (byte i = 0; i < mfrc522.uid.size; i++) 
  {
     Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
     Serial.print(mfrc522.uid.uidByte[i], HEX);
     content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
     content.concat(String(mfrc522.uid.uidByte[i], HEX));
  }
  Serial.println();
  Serial.print("Message : ");
  content.toUpperCase();
  
  
  if (content.substring(1) == "43 F0 DC 31") //to find card uid go to the serial moniter, scan your card and copy uid into the section

  {
    
    Serial.println("*** has entered");
    Serial.println();
    delay(3000);
  return;
  }

  if (content.substring(1) == "B1 F6 5B 19") //to find card uid go to the serial moniter, scan your card and copy uid into the section

{
 Serial.println("*** has entered");
    Serial.println();
    delay(3000);
}


if (content.substring(1) == "63 3C 3F 31") //to find card uid go to the serial moniter, scan your card and copy uid into the section

{
 Serial.println(" **** has entered");
    Serial.println();
    delay(3000);
}
} 

Any Help would be much appreciated