This question is misleading, I’m not sure you understand how Themes/Plugins work. It’s not that you have a plugin inside the theme. Rather the theme has plugin like features (or custom functionality).
I personally find this to be bad practice and prefer when themes come with plugins instead of trying to bundle it all together.
For what it’s worth from looking at the source I can see the the slider plugin appears to be layer slider available here. You may also be able to extract it from the theme but often this turns out to be a giant pain.