I think those fans are not controllable from OS, only from BIOS, according to this answer in Lenovo support forums: https://forums.lenovo.com/t5/ThinkStation-Workstations/Fan-Control-on-ThinkStations/m-p/5014686
You can try with FanControl.
https://github.com/Rem0o/FanControl.Releases
If not even FanControl can detect them, there is nothing to do, because their signal is not exposed from the hardware to OS.