What are the PCIe-1 connectors?

If you need to use a PCI card in a PCI-E only machine a solution pci slot 1 Mini-tower computer with 1 PCI, 3 PCIe slots Up to 2 COM Ports and 12th Gen Alder Lake, supports Windows 10 and 11 pciex1 slot One more detail: the motherboard is SuperMicro X10SRi-F that provides 6 PCI-Express slots: 1 PCI-E ×2, 1 PCI-E ×4, 2 PCI-E ×8, 1 PCI

pci slot 1 What is it and how can I use it? (With 1-slot GPUs, other connectors are visible, including one which is probably the old PCI connection