Fix conflict between FB pixel and API

Have a shopify store. Have been given this message from Facebook, Update the event_id parameter for your Purchase events so that each unique event instance is sending a unique event ID from both your pixel and through the Conversions API. For pixel, you can do this on your website's source code. For Conversions API, you can do this in Graph API Explorer or on your server terminal.
We are getting a conflict between API and Pixel and FB is not getting the correct data to optimise Conversions. Need a FB and Shopify expert to fix the issue do the code