Thank you.In the last two photos you can see pointing directly into the camera an empty female connector with THREE hols and two small ridges along its top edges. THIS is a 3-pin fan connector - that type of connector is ONLY on fans. ALSO, big clue, the cable from it to a fan has THREE wires, unlike many others. You can see the cable and connector clearly on the REAR fan. So, try to follow the three-wire cable from that empty 3-hole connector back toward the fans.
You NAY find this, and at first it can be confusing. But this has been common for older 3-pin fans. SOME of then come with a 3-wore cable that ends in TWO connectors in parallel. One of them is that standard 3-pin female (the open one in the photos). The other on the same fan cable is much wider with FOUR pins, even though only TWO wires will be connected into it. This is the male version of a 4-pin Molex power connector. The female version of it with 4 holes is coming directly from the PSU. You can actually see two of these empty in that last photo on the far right. Such power outputs used to be used as power for things like HDD's and optical drives. But many of those now use a different one called a SATA power output, leaving the Molex ones unused. Anyway, the idea of this fan with two connectors is that you can use it EITHER way. You choose one place (but not both) to plug in the fan - either to a Molex female from the PSU, or to a mobo male fan header. In your case there are NO fans connected to the CHA_FAN1 header at top front, so those three front fans MUST all be connected to PSU output(s). Now, it is ALSO possible that you will find a variation of this. The 4-pin Molex connector on the fan's cable MAY have a female (with holes) on its opposite end so that you can STACK the connectors of several fans and plug them all into ONE female output from the PSU.
You may need to undo that cable tie to free things up and trace the fan cables. But knowing what to look for may help you find them and identify.
I will check the cables more after the weather stops being this hot. My room is like a sauna right now.
By the way, can you answer my last question in my previous post?