Which function represents a horizontal shift of f(x)=5^x by 4 units to the right?

If you have a function y = f(x), the transformation along the x-axis is given by:

y = f(x+a) ⇒ This is the translation to the LEFT by 'a' units
y = f(x-a) ⇒ This is the translation to the RIGHT by 'a' units

So you have, f(x) = 5ˣ, translated 4 unit right will give g(x) = 5⁽ˣ⁻⁴⁾