Hey Deepa, if you want to submit a form on a webpage and submit button can't be identified, then in that case you can use any element of the form to submit it. Selenium webdriver find the form for us from the web element and then you can use that element to submit the form. Below is an example for it:
//Enter username
driver.findElement(By.id("username")).sendKeys("rajan.sharma@gmail.com");
//Enter password
driver.findElement(By.id("password")).sendKeys("password123");
//submit form
driver.findElement(By.id("password")).submit();
/* In this piece of code, id of password input box is used to identify a form. */
Check out this Selenium Course to learn more about the Webdriver.