Scoring points for knocking down objects

I am currently working on a little game for school where i am knocking down Orcs off a platform and i want my score on my GUI Text to go up when they hit the ground. I have the GUI text in place in the top center of the screen and everything seems to be in order, i just don’t know the exact C# code i would be entering to get this dream to become a reality.

All of my Orcs are on a separate “Enemies” layer to help with the process. I just want my score to go up by 10 for every Orc knocked off the platform and stay that way when you load in to the next level.

I have everything there. the score text is on the top of the screen like i want it, and i can manually add numbers in to it and see them displayed on the screen. i just need it to know to add the points every time one of my enemy objects falls off the platform. Maybe something like "If “Orc” goes past (Insert x, y, z, here) + 10