Hey @Rishab, you can take a look at the following code.
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
public class AmazonShoping {
    public static void main(String[] args) throws InterruptedException
    {
        //You mention the path to your chromedriver or geckodriver
        System.setProperty("webdriver.chrome.driver","C:\\Users\\priyj_kumar\\Downloads\\chromedriver.exe");
        //Create an instance of your chromedriver named driver
        WebDriver driver = new ChromeDriver();
        //Open facebook
        driver.get("https://www.facebook.com");
        //Create an instance of select and specify the webelement
        org.openqa.selenium.support.ui.Select dropdown = new org.openqa.selenium.support.ui.Select(driver.findElement(By.id("day")));
        // 1. You can select by value
        dropdown.selectByValue("6");
        // 2. You can select by index, you need to verify the index as it starts with 0 or 1
        dropdown.selectByIndex(6);
        // 3. You can select by Visible Text
        dropdown.selectByVisibleText("6");
    }
}
Hope this helps you.