Film Director said to the actor: “In this shot/show, you have to fall down into the pond
from 100ft.”
Please correct the sentence.

It is passable. Fussy people would write “100 ft”. Also, the word “down” is arguably surplus to requirements.

Obviously “show” and “shot” mean different things.

In shooting the film, what terminology do they use to describe the action of taking films such as falling into the pond from 100 ft.
Do they say it is a shot or a show or what?

A “show”, in the relevant sense, is normally a TV programme made for entertainment. When in my original response I implied that “show” was OK, I overlooked that fact that it was a film director speaking. In fact, you would not normally use the word “show” to refer to a feature film (i.e. something you might go to the cinema to see).

A “shot” is a short filmed sequence showing a single event. Falling into a pond would likely constitute one “shot”. The word “scene” would probably also work in your sentence. A “scene” is an episode of a film, typically consisting of a series of shots taken in one location.

A “shot” should not be confused with a “shoot”, which refers to the general process or activity of filming or taking photographs.