'pip' is not recognized as an internal or external command, operable program or batch file.

py -m pip install [packagename]

python -m pip install [packagename]

This is probably caused due to Python not being added to the
Windows path. To add Python to the Windows Path, follow these
steps:

1. Start the Run box and enter sysdm.cpl
2. In the System Properties window go to the Advanced tab and 
   click the Environment Variables button
3. In the System variable window, find the Path variable and 
   click Edit
4. Position your cursor at the end of the Variable value line 
   and add the path to the python.exe file, preceeded with 
   the semicolon character (;)