I am assuming that you have installed python in your machine already. To install pip3 follow the steps below carefully:
Open your terminal and follow these commands sequentially.
sudo apt install python3-pip
pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6)
Congratulation. You’ve installed pip3 on your machine.
In case you are using a Windows-based OS:
1) you can download python again on the official website;
2) Navigate to the directory where
"Python 3.7 (64-bit).lnk"is located
import ssl and
4) type in cmd,
"Python 3.7 (64-bit).lnk" -m pip install tensorflow for instance.
Here, you're all set.