On Linux systems there is no need to search the network for additional programs or extensions of the applications, because often they are already in a batch system cache, but not installed due to the fact that the majority of users are simply not needed.
Consider 3 options to install additional packages to your desired programs:
-Software manager (Graphical method)
-Synaptic Package Manager (Graphical method)
-Terminal (Console method)
1. Software manager (Graphical method)
Open Software Manager in the search bar enter the package name of the desired program (e.g. nemo or gimp) and press Enter. You will only need to choose the desired extension and click Install. (To apply changes in the system applications will likely require a system reboot).
2. Synaptic Package Manager (Graphical method)
In my opinion, a more convenient way. The principle is the same. Select the package. Mark for installation and click apply.
3. Terminal (Console method)
To search the apt cache, there is a special and quite simple command: apt search package. To search for extensions in Nemo it would be the following:
apt search nemo
The i flag means that the package is already installed. The p flag means that the package is available for installation:
Make and run command:
sudo apt install nemo-dropbox nemo-image-converter gtkam-gimp gimp-ufraw
Don't worry, if you copied to install an extension that is already installed in the app. The terminal will tell you about this.
In this article, for example, I chose the apps that system installed on my computer, but search and install extensions for other programs and file managers (Caja (file Manager for the Mate environment), Thunar (file Manager of the Xfce environment)) is identical.