Thanks for writing in!
Both the slider plugins or any of the extension coming with the theme doesn't need a purchase code to validate or active.
You just need to validate the theme and install and active the plugins via Dashboard -> X/pro -> Validation.
If you have any error during installation and active, you can send us the error message screenshot so that we can have a look.
There is no need to validate the plugin separately, if any extension giving a message regarding validation, you can simply ignore it.
Please check for more clarification.