how to install virtualenv on Ubuntu 20 04 GCP instance

Question

I am trying to install python3 virtualenv. I often get the below-mentioned message whenever I try to run virtualenv.

virtualenv
Command 'virtualenv' not found, but can be installed with:
apt install python3-virtualenv

but if I run install command, I get the following error.

apt install python3-virtualenv
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package python3-virtualenv

For python3 -m venv, I get message to install using apt-get install python3-venv but when I try it, I get the same message.

sudo apt-get install python3-venv
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package python3-venv is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'python3-venv' has no installation candidate

I am running this as root. wget also works.