You can create sources.list
in /etc/apt
directory.
sudo touch /etc/apt/sources.list
Open file with nano.
sudo nano /etc/apt/sources.list
Copy following content in file.
#------------------------------------------------------------------------------#
# OFFICIAL UBUNTU REPOS #
#------------------------------------------------------------------------------#
###### Ubuntu Main Repos
deb http://in.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse
###### Ubuntu Update Repos
deb http://in.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://in.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse
Save it and You will be able to run
sudo apt update
and install any packages.
dpkg -S /etc/apt
and install them usingdpkg -i
. You may need some help from How can I restore the default repositories and I'm not sure this will work.