pci-e 8 pin connections

Good afternoon to all, I am upgrading my desktop awaiting receipt of AMD Ryzen9 3900 3.8 ghz and subject graphics card. The now installed graphics card (soon to be old - ASSUS R9-380) has 2 PCI-E 6 pin connector (PSU-PCI-E) cable having 2X6 plugs and 2 spare/floating 2 pin plugs that aren't...