Bizarre issue with fitting the GPU into the PCIe slot

PCIPCIe Card Installation pcie slot cover I'll get straight to the point, is there an easy way to know what PCIe slot on a mATX motherboard lines up with what slot on a case? pcie 30 in 40 slot Pub Smart Magnetic Absorb Lock The Fan Easily7 Pcie Slots Glass Side Computer Case, Find Details >and Price about RGB E-ATX Large Motherboard,

pciex16 slot 2 slot In the case of SSDs, it is becoming less and less popular and is being replaced by PCI Express HDDs continue to rely on the SATA