CentOS Core Enterprise does not come with PIP in repositories. Thus you need to turn on epel release in order to find pip packages
sudo yum install epel-release
After this you will be able to install pip via following commmand
sudo yum install python-pip
Another call-out, by default it is Python2. You can install python3 and pip via:
sudo yum install python3-pip
sudo pip3 install --upgrade pip