Just to make sure everyone knows:-
Gcode is the movement of the print head ( XYZ ) , extruder and platform tempretures.
This depends on the 3d printer specifications, the set layer height and the print filament.
Converting STL to GCODE is the job of the slicer that knows the printer ( and your ) preferences as well as the material. STL is the preferred export from 3D software to import into a slicer.
The most popular is Cura ( the one you are using now ) which is also free, i personally use simplify3D as I have 5 3D printers and they all have there tweaks.
A good list of slicer software is here: https://all3dp.com/1/best-3d-slicer-software-3d-printer/