Did you first determine your active Python location for Scripts according to bottom of the documentation here?
where
Scriptsis located in the active Python’s installation location.
You replace Scripts in that command with that location, I think.
Here has an example in an image under the text ‘And this is how my Python Scripts path looks like:’ showing where the installation was in that Windows example.
This post with the same error spells out the command that actually worked with a similar path. You’ll see in that example there they first used cd to change to location of Scripts and then issued the following while in that directory:
python pywin32_postinstall.py -install
Just noting here mainly for others in a similar boat (and for keeping related topics linked here) that also this thread that lead to this suggestion has an error in the original post looks similar to yours.
But I demoted mention of it because you look well on your way to reinstalling pywin32.