Start Button > Right Click Properties >Advanced system settings > Advanced Tab > Environemnt Variables > user varibales > Look for a variable called path, if if is there edit, if not new:
Variable Name: path Variable Value: (separated by ; if on windows 7, new entry on windows 10) C:\Python27\ArcGIS10.3\Scripts C:\Python27\ArcGIS10.3
Open comand promt (cmd)
python
Should return python version
python -m pip help install
Should return pip help
pip: https://pip.readthedocs.io/en/latest/installing/
If you have numpy and you can not upgrade or uninstall it with pip it was installed by another method. Delete it's references from: C:\Python27\ArcGIS10.3\Lib\site-packages
From the comand prompt:
python -m pip uninstall numpy
python -m pip install numpy==1.16.5
Successfully installed numpy-1.16.5
python -m pip install pyyaml
python -m pip install psycopg2
python -m pip install archook
Successfully installed pyyaml-5.1.2 Successfully installed psycopg2-2.8.4 Successfully installed archook-1.2.0
To make sure you have the latest version download a new version and install from file:
python -m pip install C:\Temp\fgdb2postgis-master
This will install the package at: C:\Python27\ArcGIS10.3\Lib\site-packages