How to apply OnBecameInvisible

Salutations Unity Community,

I'm a beginner, so bare with me.

I'm developing a infinite runner of sorts and I'm very new with C#. One of the most import functions I'll need to use is OnBecameInvisible and I've so far been unsuccessful at applying it to any of my prefabs.

I have a simple moving camera that follows a primitive object. My prefabs generate in front of y camera, but never destroy when they pass the character.