Upgrade python from 3.8 to 3.9

I have manually downloaded the latest python upgrade - 3.9.6, however when I check the version of python on my terminal (iMac - big Sur):

-iMac ~ % python --version
Python 3.8.8

However, when I try to upgrade my python using home-brew:

~ % brew upgrade python
Warning: python 3.9.5 already installed

I seem to not have the one that I downloaded - python 3.9.6. Is there a way to remove these other python languages i.e. 3.8.8, 3.9.5 and just keeping the latest python 3.9.6?