hi i bought a ryzen 5 3400g cpu, could you plz guide best suitable motherboards
ASRock X570/X470 chipsets are a good choice.
I'm personally going with the ASRock X570 Taichi mobo.
Those chipsets are good because they'll ensure 'future-proofing' for a couple of years. It was announced that the 4xxx series of processors would maintain the AM4 socket, therefore you might as well go all out on your motherboard as you can have it for quite some time and only choose to upgrade the other hardware you have.
The Asrock B450 Gaming k4 has support for Ryzen 3000 out-of-the-box so speak with the retailer first to confirm that they have the new version and not the old. That motherboard copes with the heat from a 16-core 32-thread Ryzen 3950x.