I tried these commands.
aayush-parajuli@aayush-Inspiron-15-3567:~$ sudo apt install gnome-shell-extensions
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package gnome-shell-extensions 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 'gnome-shell-extensions' has no installation candidate
aayush-parajuli@aayush-Inspiron-15-3567:~$ sudo apt install gnome-shell-extension-prefs
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package gnome-shell-extension-prefs 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 'gnome-shell-extension-prefs' has no installation candidate
