to find your MoBo you need to look inside your PC
usually it is written anywhere near the first PCIe Slot
than when we know WHAT your MoBo is we can find out if it will support Ryzen 9 3900X
PC: R7 2700X @PBO + RX 580 4G (1500MHz/2000MHz CL16) + 32G DDR4-3200CL14 + 144hz 1ms FS P + 75hz 1ms FS
Laptop: R5 2500U @30W + RX 560X (1400MHz/1500MHz) + 16G DDR4-2400CL16 + 120Hz 3ms FS