The transformation from \( f(x) = x^2 \) to \( g(x) = (x - 3)^2 \) involves a horizontal shift. The general form of a quadratic function \( f(x) = (x - h)^2 \) indicates a horizontal shift by \( h \) units.
In this case, since \( g(x) = (x - 3)^2 \), the function \( f(x) \) is shifted 3 units to the right.
Therefore, the correct statement is:
Function f was translated (shifted) horizontally 3 units to the right.