How to move all modules to new version of Python (from 3.6 to 3.7)
I faced a similar problem, now that I upgraded from python 3.7 to python 3.8 (new)
I installed Python 3.8, but the system kept the python37 subfolder with the already installed packages(...\Python37-32\Lib\site-packages)  even with the  Pyhton38 subfolder created, with the new python.exe.
Usually, it's possible to keep on using the old libraries on your new Python version, because the existent libraries installation folder are already registered in your local computer  system path (*).
Even though, I've had problems to use some libraries (some worked  in Jupyter Notebook but not in Spyder). I tried the alternatives others proposed to migrate libraries  but it did not worked (maybe I did not
So I used brutal force solution.. Not elegant at all, but it worked:

remove the OLD python version folders from the system path  or even remove the folder itself for good..
Folders:  C:\Users\USERNAME\AppData\Roaming\Python\Python37
C:\Users\USERNAME\AppData\Local\Programs\Python\Python37

Reinstall the packages you need, preferably via Anaconda prompt.
python -mpip install library_name
OR
pip install --user --force-reinstall package_name
OR
pip install --user --force-reinstall package_name == specify_package_version


The libraries will be installed  at  c:\users\USERNAME\anaconda3\lib\site-packages and recognized by your new python version.
(*) to add the folder to the PATH:  System properties --> environment variables --> click "Path"--> edit --> add folder name)
I just upgraded to python 3.7 and I realized that all my modules stuck with the previous version. Even Django is not recognised anymore. How can I do to transfer everything to the new version? I am a little lost right now, don't even know where the new version has been installed.
Edit:
When I do $ which python3.6 the terminal tells me it doesn't exist, but I have a python3.6 directory in /usr/local/lib/, where all modules are installed.
In the same directory /usr/local/lib/ I also have a python3.7 directory with some modules installed but many are missing. However when I search for the file python3.7 in my finder it doesn't appear. when I do $ which python3.7 the path is /usr/local/bin so not the same path as the directory.
Anyone sees what happened and knows how I can transfer all modules to python3.7?