Don't buy anything below 3200MHz ram for ryzen 3xxx.
It depends on the combination of mobo(more specifically bios)+ram+processor.Isn't it that it's the motherboard that has to support memory at a certain frequency? The motherboard I listed above supports upto 4000 MHz.
You can run ram at 3000-3200MHz with ryzen 1st gen depending on mobo bios & ram model using manual overclocking.I used to think that, but even the generation of CPU matters. My mobo supports upto 3200mhz but 1st gen ryzen 5 only supports upto 2666mhz