Is there any alternative way to bring a AGP(8x)graphics card works in a PCI slot ?

Sorry...there are no "riser" adapters to do what you want. The cards are specific to their respective slots. A PCI card in the PCI slot would be slow as compared to an AGP card in the AGP slot. BOTH would be slow as compared to a PCIe X16 card in a PCIe x16 slot. To boost your video card and its performance you would need to buy a mother board and video card for PCIe x16