Answer
$$
f^{-1}(x)=\sqrt{x}+1
$$
Work Step by Step
Given $$ y=x^{2}-2x+1$$
Find the inverse:
\begin{aligned}
& y=x^{2}-2x+1\\
& y=(x - 1)^2\\
& \Rightarrow x-1=\sqrt y \\
&\Rightarrow x=\sqrt y+1, \\
&\text{Switch $ x $ and $ y $}\\
&y=\sqrt{x}+1=f^{-1}(x)
\end{aligned}