Answer
please see image below (f(x)=red curve, g(x)=blue curve),
asymptote of $ f:\quad y=0$
asymptote of $g:\quad y=0$
Work Step by Step
Graph $ f(x)=3^{x}\qquad$ (red)
by plotting the points from the table and connecting with a smooth curve.
$g(x)=3^{-x}=f(-x)$
so the graph of $g(x)$ (blue) is obtained by
reflecting the graph of f(x)
about the y-axis.
Reading the graph,
asymptote of $f:\quad\quad y=0$
asymptote of $g:\quad\quad y=0$