WebUpd8 do try their best to adapt most important Gnome-Shell extensions for Ubuntu, and have already put three of MGSE extensions in their repository. Unfortunately, the one you want is not there yet.
So, you may want to get it from their GitHub branch.
1) Install git:
sudo apt-get git
2) Create a folder where you want to put all Git repositories
3) cd to that folder and use git to create a clone:
git clone https://github.com/linuxmint/MGSE.git
Later to update use
4) When everything is done, it will create a separate folder MGSE. So, cd to that folder. You will see a bunch of folders containing an extension each. There is a file called test to install all of them at once, and there is also one file test in each folder to install one particular extension. Run either one depending on what you want.
I do not recommend installing all their extensions at once. To avoid conflicts in your system and keep it stable, install only those not available, or at least, not installed through other repositories such as WebUpd8 Gnome3 PPA.