This is metric is a custom metric, called a success event, that is specific to your site. My best recommendation is for you to work with your administrator and implementation team to figure out how and when this metric is called.
Based on how it was named, I'm guessing it's captured in event9. If you want to try and find out how it is populated on your own, you can use the Experience Cloud Debugger to find event9. Here is a helpful video on using the Debugger: How to Use the Adobe Experience Cloud Debugger