how to change "confirm button" in checkout step6

hello.. Sir..

  hello sir i am recently create my account, i have a few questions in opencart. so plz help me.. sir i want to change "Confirm Button" in checkout last step6.. there is right side shown "confirm order" button i want to change this button.. but how.. i don't know.. so plz help me.. i attached some screen shot check this.. 

   thanks in advance.....