I would just recommend creating a new virtual environment and installing all the packages from the start as the wheels for some packages might have been installed for the previous version of the Python. I believe this is the safest way and you have two options.
Creating a new virtual environment with venv
:
python3.6 -m venv -n new_env
source venv_env/bin/activate
Creating a conda
environment:
conda create -n new_env python=3.6
conda activate new_env
The packages you install in an environment are built based on the Python version of the environment and if you do not carefully modify the existing environment, then, you can cause some incompatibilities between packages. That is why I would recommend a using a new environment built with Python 3.6.