[SOLVED] Question for ASRock b450m Pro4

Solution
16GB is plenty. 3000-3200 MHz is a good speed. Get something on the motherboard memory qvl list if you want to be extra cautious about the memory being able to run at its rated speed without any fiddling.
It can support up to 64 GB. https://www.asrock.com/mb/AMD/B450M Pro4/#Specification

It's not clear to me if you're planning on combining the new RAM with your current RAM, but I will say that combining RAM that was not purchased as a single kit is not guaranteed to work together. It can be unstable, refuse to run at full speed, or require manual tweaking.

What will this PC be used for? 16GB is plenty for most use cases.