Hi,
While installing Python 3.8 there was a box [ Add python 3.8 to path], you have to check that box while installing. If you don't check that box you won't be able to execute python files or packages anywhere from the system and it will not be recognized from the command prompt.
To check you have installed the correct python version, here goes the command to use in the command prompt:
python -v
This will show you the correct python version on your system.