Opencart - Add Tracking Code for Shareasale

I need someone to implement the shareasale tracking code into my opencart website. The tracking code is: <img src="[login to view URL]" width="1" height="1"> This should be placed in the HTML body of the "Thank You" page after checkout. It is required to write some code so that these values in the tracking code can be replaced by the opencart system. These include: 1. The subtotal amount of the sale – referred to as the AMOUNT 2. The order number or unique identifier from that order – referred to as the TRACKINGNUMBER