Venv

You could use a virtual environment (venv) for installing dependencies.
This venv could be project specific or global.

Run python3 -m venv .venv in your project folder to create a .venv folder, which holds the venv configuration.

Run source .venv/bin/activate to activate the venv. This will link pip3 from your python 3.9 version to the pip command.

Now you can do pip install pandas to install the pandas dependency into the venv.

Conda

Another solution would be to use Anaconda or Miniconda

https://pandas.pydata.org/pandas-docs/stable/getting_started/install.html

 conda create -n name_of_my_env python

This will create a minimal environment with only Python installed in
it.

To put your self inside this environment run:

 source activate name_of_my_env

On Windows the command is:

 activate name_of_my_env

The final step required is to install pandas. This can be done with
the following command:

 conda install pandas