To find your Custom Conversion metrics in the manage section of AdStage:
Step 1: Navigate to Facebook, via the Networks tab
Step 2: Click into the account with Custom Conversions
Step 3: Find the "Select Columns" pull-down - Located at the top right of tables
Step 4: Scroll down or search (Filter Columns) for your Custom Conversion metrics
Learn how to add Facebook Custom Conversions to Report here.
*How do I find my Standard Conversion metrics? click here