Make one MacBook Pro use the screen of another MacBook Pro
Solution 1:
You can't physically connect the display of another MacBook (or any other laptop for that matter) to use it as an external monitor.
However, there is an app called AirDisplay that will turn any display into an external monitor via WiFi (or wired network if you prefer).
Wirelessly connect to an iPad or Android device from your laptop to create the ultimate road-warrior workstation. Or repurpose any nearby Mac or Windows PC to give yourself more screen real estate for your main Mac.
It's a pretty good piece of kit, but (IMO) it's better to just purchase an external monitor that meets your needs; it's much more stable, reliable, and better performing.
Solution 2:
According to this Apple web site, only the following iMac models offer Target Display Mode.
- iMac (27-inch, Late 2009)
- iMac (27-inch, Mid 2010)
- iMac (Mid 2011-Mid 2014)
There is no mention of any Mac Book Pro models that can be used as monitors.