How to filter by query string in Google Analytics?
First, you should probably be using UTM parameters for offsite campaigns. Google Analytics automatically pulls UTM campaigns into standard campaign reports so youd have to do only minimal sorting and filtering to analyze your Facebook ad performance.
But since you used a custom query string instead of UTMs youll probably have to create a Custom Segment: Advanced > Conditions, and Include only Users (or Sessions, up to you) who hit a Landing Page that contains src=fb. Like so:
Save that segment and view your reports through it and as long as your property is configured properly (you may have to define goals), you should see how your users behaved after hitting the ad.