This menu is made by ProModz

Its a Map Mods menu meaning like custom ramps
and other stuffs

Menu does not have a car spawner but you can do this

Once you are loaded on GTA 5 inject ProModz.xex
via Module Loader, can use PC or stealth server you are on
should have one, make sure you inject when you are loaded
not when loading meaning when you are literally playing as
any of the protagonish Franklin,Michael or Trevor and menu should load

So to get cars spawning you simply inject another XEX menu
once you have injected ProModz.xex

For me Online crashed but may work for you so yeh thats it

Text by - aciph