In this post, I will not tell how to install the plugins via normal way like installing using Jenkins install plugin menu under manage Jenkins.
In this, I will tell you an unusual way to install the plugins for those who have already have the plugins in existing Jenkin now they want to replicate in another instance of Jenkins or you have already a set of the plugins.
Where are the plugins in the existing installation?
First, you need to find out your Jenkins installation directory of the existing Jenkins installation.

Install plugins:
In Jenkins’s home path there is a plugins folder. Go to in plugin folder copy all *.jpi or *.hpi file from there. OR if you have already set of plugins copy them.
Now go to Jenkins’s home path of the new installation. Find out plugin folder, if it is not there then create that folder with name “plugins“
Now paste all copied plugins into the plugins folder.
After successful paste of plugins, now restart your Jenkins. If everything went fine then you can see all your plugins available in your new Jenkins setup.