Is this possible?

I have an old ASUS MOBO and it has 2 PCI slots. Is it possible to get a PCI to PCIE card (1x) and then a riser 1x-16x to squeeze in 2 more GPUs? I'll have a 2nd PSU to run the 2 GPUs, the model is P5G41 M-LE.

I found an adapter already: https://www.amazon.ca/Startech-Com-Express-Adapter-Card-PCI1PEX1/dp/B0037ECAM21