I would start on KUKA's site since your questions would be specific to it, while ST is general and the same for all PLC vendors (IEC 61131-3 standard).
Does the KUKA code employ Beckhoff's Numerical Control option? If so, you will see things under the "NC" heading in the Project Tree (within Visual Studio). The NC implementation is specific to Beckhoff and comes in ~3 varieties, I think the lowest level being a basic G-code interpreter for 3-axes.