Hello and welcome.
You can't enable Full Screen mode in Finder itself, only in applications that support it. When an application supports it, the View menu option will be available.
In Finder and system-wide, you can set the Dock to automatically hide/show in > System Preferences... > Dock > Automatically hide and show the Dock. The menu bar is permanent and cannot be hidden, except when in Full Screen mode within an app.
Hope that helps.
C