Noob, not really sure what my problem is: (Python, pytest, pytest-cache, stupidity, versions)

I´m all new to exercism, but I like the idea. I´m using MacOS.

I have followed the walk-through to install the CLI, and I´m pretty sure I managed to do so. I have also downloaded Python3 and pip3 to be updated. (I used to have Python 2.8 before).

When I run list for pip3, it lists pytest and pytest-cache (among other) with the right version number, but when I try pytest --version, it tells me that it is not installed. (Command not found)

So I kept trying different things, and at some point I checked the version for Python. I don´t actually know if that has anything to do with anything else, BUT... When I did it told me I had Python version 2.8 in the terminal.

When I open IDLE, I have a nice new version (3.8.1), so I´m puzzled right now.

Summary: I can´t run my tests, since pytest don´t seem to run properly. (If things work out after that step, I don´t know.)