Step 1 :First, we need to find the function $f(x)$ such that $h(x)=f(g(x))$. Since $g(x)=3x-14$, we substitute the values of $h$ into $g(x)$ to find $f(x)$.
Step 2 :We have $h=\{(0,8),(2,-8),(7,2),(8,4)\}$ and $g(x)=3x-14$. So, we get the following pairs: $(g(0),8)$, $(g(2),-8)$, $(g(7),2)$, $(g(8),4)$ which simplifies to $(-14,8)$, $(-8,-8)$, $(7,2)$, $(10,4)$.
Step 3 :From these pairs, we can see that $f(x)=2x+22$.
Step 4 :So, $h(x)=f(g(x))=2(3x-14)+22=6x-28+22=6x-6$.
Step 5 :Let's replace $h(x)$ with $y$ for simplicity, so $y=6x-6$.
Step 6 :In order to invert $h(x)$ we may solve this equation for $x$. That gives $y+6=6x$ or $x=\frac{y+6}{6}$.
Step 7 :Writing this in terms of $x$ gives the inverse function of $h$ as $h^{-1}(x)=\boxed{\frac{x+6}{6}}$.