From the menu, start the "Package Manager" and search for "screensaver."
In the Linux world, you will not find gobs of screensaver programs available for download from everyone and his brother as you do in Windows world. Which is just as well, because many of the free Windows screensavers come at the cost of your privacy, at the least.
By default, Mint comes with the Gnome screensaver, which can be accessed from the "Control Center," and includes dozens of screensaver choices.
As a matter of routine, I remove the Gnome screensaver and replace it with xscreensaver, which is easier to configure and contains more choices. If you wish to do that, do some research first.