You can use \textsuperscript{...} outside of math mode to do this. For example:

n\textsuperscript{2} for n-squared,

n\textsuperscript{th} for n-th.

My understanding is that both \textsuperscript and \textsubscript used to be part of the fixltx2e package until 2015 when they and some other commands were added directly into LaTeX so no package was needed.

I'd suggest to use $....$:

\documentclass[a4paper, ngerman, 12pt]{scrreprt}
\begin{document}
This is a blind text trying to write exponents in a textline. $a^{2}$  This is a blind text trying to write exponents in a textline.

$a^{2}$
\end{document}

The first part of the code gives you an exponent during textflow. The second part creates an exponent on the left.