Answer
$g(x)= \sqrt {-x+3}+2$
Work Step by Step
Let the final function be $g(x)$.
Start from $f(x)=\sqrt x$
(1) Shifting up $2$ units gives $f(x)+2$ or $\sqrt{x}+2$.
(2) Reflecting about the $y$-axis gives $f(-x)+2$ or $\sqrt{-x}+2$.
(3) Shifting left $3$ units gives $f(-x+3)+2$ or $\sqrt{-x+3}+2$.
Thus, $g(x)= \sqrt {-x+3}+2$.