According to the manual for that mobo, on p. 1-22, the SYS_FAN1 header MAY be able to control a 3-pin fan. It is not using PWM Mode, so it MAY be using Voltage Control Mode. The SYS_FAN2 header apparently does NOT control any fan.
Make sure one of your fans is plugged into the SYS_FAN2 header and observe it carefully. IF it is under control, you will see it start up at full speed when the machine is turned on from not being in use, but in VERY few seconds it should slow down, them slowly speed up as your system is used and warms up. If it does that, your mobo can control 3-pin fans on this header only. Buy a splitter that has two output arms (it may be for a 4-pin fan system, but it will work). and use it to connect both your fans to this header.