Not installing pip on ubuntu 20.04 [duplicate]

Tried -

sudo apt update

sudo apt-get install python3-setuptools

giving error -

E: Package 'python3-setuptools' has no installation candidate

Tried -

sudo apt update

sudo apt install python3-pip

giving error -

E: Package 'python3-pip' has no installation candidate

When checked for universal repository -

sudo add-apt-repository universe

'universe' distribution component is already enabled for all sources.

For any other command too, giving error as python3-packagename has no installation candidate.

I checked the version of python, it is 3.8.2 . I installed 3.9 now and how to make it default. I want to try it so that whether it may works.

Run

sudo nano /etc/apt/sources.list

And add these lines.

deb http://archive.ubuntu.com/ubuntu bionic main universe
deb http://archive.ubuntu.com/ubuntu bionic-security main universe 
deb http://archive.ubuntu.com/ubuntu bionic-updates main universe

Press Ctrl+O to save the file. Press Ctrl+X to quit nano.

Then run:

sudo apt update
sudo apt install python3-pip

This works.
I also works with

apt update
apt upgrade