Atmel SAM3X / SAM3A, handle interrupts from Parallel Input/Output Controller (PIO)

Question

I want to enable the PA8 pin in a processor (Atmel SAM3X / SAM3A). I have set PIOA_MDERp[7]=0 and PIOA_MDDR[7]=0 and PIO_OER[7]=0 and PIO_ODR[7]=1, so that the tri-state buffer will no longer send data out of the pin, and the pin is enabled to receive data from the environment and to send interrupts if needed. I also want to set my interrupt to rising edge, so I also did PIOA_RHLSR[7]=1 and PIOA_FELLSR[7]=0 and also PIO_ESR[7]=1 and PIOA_LSR[7]=0. My problem now is how to modify NVIC registers so that this interrupt is enabled. I mean, on a rising edge on this pin, the state of this pin is pending, and then the changes I will apply to NVIC causes this pending state to active state. My interrupt group priority and subgroup priority are both 3. I know how to modify Interrupt set-enable register, interrupt clear-enable register, application interrupt and reset control register, and interrupt priority register. Still, my problem is that now I don't have any number for interrupts from this specific pin (PIOA8), so it is different from the time I had my interrupt number (from 1 to 240), and so I could know which register in the NVIC I should modify. Thanks for your help.