How to determine which slot a SSD is connected to

2 slots are backward compatible so there is no need to worry about purchasing the wrong expansion card or NVMe SSD But you might want to save a buck or two by

Both SATA and PCIe protocols can be used with an SSD SATA is a connector and data transfer standard for hard disc drives and computer systems PCIe,

can you put 2 speaker wires in one slot No, the NVMe SSD can fit into the SATA SSD slot but it doesn't work The reason is NVMe SSD using PCIe interface

candyfinity slot If you want to use 4 SSDs on one adaptor you need to put it in a slot which gets 16 lanes