To clone a unit visit the course dashboard and click on the Add content (1) button. A drop-down menu will appear and among the available options, you shall find the Clone unit (2) option.
Clicking on the Clone unit option will open a pop-up window. This window has two drop-down options. The first one displays all available course lessons in your system (3). First, select the lesson which includes the unit you want to clone. Once you do that, the second drop-down will be available, with all units of the selected lesson (4).
Click 'Clone' to clone that unit, which will then appear among the units of your course in your course dashboard, or clone and clone another to continue with the process until you have cloned all the units you want.
So long as you don't check the "Retain relationship with original content (link)" option, the new unit stays independent of the source unit. You are then free to change its title and content at will, while the original unit remains unaffected.
Note: Consult this article to see how units linked to original content work.