Pro sites VS membership for subscription access, whats the deal?

so now I'm stuck on figuring out what does the visitors get to click on to be a paid member?

There is the pro sites in the menu bar showing all levels to subscribe too, then there is the membership subscriptions in the menu bar showing all levels to subscribe to, too?

The free subscription is set to 0.00 dollars, and I want to give them a free 3 day access without paying to checkout features before they buy? it is not working like that for me?