I seem to have two versions of python 3.7.9 installed

[Gribouillis]

You can ask python to where it points. For example in my kubuntu 16.04,

λ python3
Python 3.5.2 (default, Oct  7 2020, 17:19:02) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.executable
'/usr/bin/python3'

By the way, what about installing packages from within Python itself? You would be certain that they are installed for the current interpreter.

import subprocess as sp
import sys

def install_package(name):
    sp.call([sys.executable, '-m', 'pip', 'install', '-U', '--user', name])


if __name__ == '__main__':
    install_package('requests')