So I have a B350 AM4+ Gigabyte mATX motherboard and installed it in a Cullinan Rosewill ATX case. There is one cord called "Fan Power Controller" and I have no idea where it goes. I have a couple of pictures below of it.
https://imgur.com/TTHDQXa
https://imgur.com/8alN1Dc
https://imgur.com/orq5WrU
https://imgur.com/CGH2iJm
https://imgur.com/TTHDQXa
https://imgur.com/8alN1Dc
https://imgur.com/orq5WrU
https://imgur.com/CGH2iJm