You'd have to open up the PC and look at the power supply. Wattage is usually stated on there.
I see. I would also like to ask you bro, i read that this PC has Built In Graphics Card which is R7 Graphics, i am wondering if there will be no conflict if I will put the suggested graphics card of yours. Thanks bro.
The integrated graphics of the A10-7860k should be disabled when a discrete graphics card is installed. Some motherboards may require entering the BIOS to change the behaviour. But there is no conflict.