Hi, Lin,
I do not know if your ADC triggering signal is required to synchronize with PWM signal from your application requirement.
If it is not required, I suppose that you use ADC12 module, in the case, the ADCA trigger signal is XBAR_OUT12, you can select any signal from the Table 3-6. XBARA and XBARB Inputs in MC56F847xxRM.pdf

If the ADC trigger signal is required to synchronize with PWM signal, and all the PWM VALx are used, in the case it is complex. I do not know if the PWMB module is used, if it is not used, you can synchronize the PWMA and PWMB, use PWMB val0 register to trigger ADC, in the case, the PWMA PWM signals will synchronize with ADC triggering signal.
Hope it can help you
BR
XiangJun Rong