I don't even know what went wrong. I'm new to programming and I need this package (pymIprog) for a college assignement
You are doing a pip install in a Python 3.9 environment. I can't get that to work either: it fails trying to install swiglpk. But it does work in Python 3.8 and Python 3.7.
I can't tell you how to fix it: only the packagers of swiglpk can do that. But to get going, you could download Python 3.8, which will coexist nicely with Python 3.9, and work from there.
Python 3.9 only came out quite recently and some packagers take a while to catch up with new releases.
To be sure of running the right version of pip, begin by doing pip --version and if it is not the version you expect, run your pip command from C:\Program Files\Python38\Scripts.
