Starting with SOLIDWORKS 2019-2020, add-on products like CAM, Composer, Electrical, Simulation, Flow Simulation, etc. are included under the CAD serial number itself. You are not required to input serial numbers separately to install these products. Just enter the serial number for CAD; all other fields should be empty and deselected.
Note that SOLIDWORKS PCB, SOLIDWORKS PDM, and other server products are not part of the list of products included with SOLIDWORKS CAD. You will need a separate serial number if installing these products. SDK licenses are entitled to only SOLIDWORKS Standard products. You can find the list of features for SOLIDWORKS Standard through the product matrix at this link - www.solidworks.com/solidworks-3d-cad