To find your Facebook Conversion API Key, follow these steps:
Navigate to Facebook Business Events Manager. You can access it directly using this link: https://www.facebook.com/events_manager.
In the Events Manager, you will see a list of your available Pixels (if you've already created one). If you haven't created a Pixel yet, click on the green "Connect Data Sources" button, select "Web," and then click "Get Started." Follow the instructions to create a new Facebook Pixel.
Once you have a Pixel, click on its name in the list. You'll be taken to the Pixel's overview page.
On the Pixel overview page, Navigate to Facebook Pixel Settings by clicking the "Settings" tab
On the "Settings" tab, scroll down to Conversions API and click "Generate access token"
Copy the value of the Access Token.
This is your Facebook Conversion API Key.
Paste it into UpStackified Facebook Pixel Integration Setup
Note that the Conversion API Key is a sensitive piece of information, and you should store it securely. Also, keep in mind that the Conversion API Key is specific to your Facebook Ads account and cannot be used across multiple accounts.
Find out how to Find your Facebook Ads Pixel ID
Check out this article to find more information about setting up Shopify Multiple Facebook Pixels with UpStackified Shopify App