If PIP is not recognized as an internal or external command when trying to install Python libraries here are some suggestions to help you.

A command is not recognized as an internal or external command If you are troubleshooting a program, you need to ensure it exists. It can even happen with the RUN prompt, invoked using the WIN+R ...

This is what tells the command line which folders it needs to look in when searching for the file. If Python isn’t added to PATH, then you would need to point CMD directly to the Python.exe and ...