This may sound scary, but if ONE original 7-year-old fan has its bearings worn out, then ALL of three are nearly worn out, and all three should be replaced. But once out figure out how to do one, the rest will be easy! Let's look at the steps.
Background info. Fans basically come in two different designs, with several sizes for each. MANY modern fans also come with lights built into the frame, but you do NOT have any of that type, and you should not change to this variety. The older fan design is called 3-pin or Voltage Control Mode fans, and that is what you have. If you look at those fans (it's visible in the photos), each has a cable from it with THREE wires in it. If you follow each to its end you'll see a connector about 3/8" wide with a couple of ridges running down one side. If you unplug that momentarily you will see it has THREE holes to fit 3 pins on the other part of the connection. The little ridges fit around a "tongue" beside the male 3 pins so you can only plug it in one way. The newer fan design uses 4 wires and pins and holes and is called a 4-pin fan or PWM Mode fan. You do NOT have this. Further, that fan needs a different type of mobo fan header you do not have, so do NOT get 4-pin fans.
You need power AND speed control for your fans, normally provided by a mobo fan header. Your mobo has three headers in total, but one of them is the CPU header at top centre to be used only for the CPU chip cooler. The other two are CHA_FAN headers - one right next to CPU_FAN at the top, and another below and to the rear from the CPU chip socket. You say you know the REAR fan is plugged in and where, but do not know how the two front ones are connected. I suspect the rear one is plugged into the CHA_FAN2 header closer to it. So MAYBE the two front fans are connected to that CHA_FAN1 header at the top beside CPU_FAN. Is there something plugged in there? If so, try following that cable and you MAY find it meets up with the TWO cables from your front fans. If so, then you have found the connections AND know how to connect any replacement units. Post back here what you find so far.
I'll do details later, but very briefly this is what you will do. Buy three identical fans (I'll provide some details to choose the right ones). For EACH fan you disconnect its cable from its power source and untangle it from the rest so the cable is free. Then from OUTSIDE the case you unscrew the four screws that turn into holes in the corners of the fan frame and this frees that fan for removal. Installing the new one is just the reverse using the same mounting screws. One small note here. the holes in the frame of the new fan are NOT pre-threaded so the screws have to cut their own new threads in the frame plastic. This takes some twisting effort, it is not super easy, so don't be alarmed.
Let us know what you find so far, and we can proceed with full remaining details.