Unless replacing you memory completely you should buy the same ram you already have. I would open up the pc and take a look at the existing brand , get the serial number off it and find that exact one.
Your motherboard does not support ddr4 and only supports upto 16gb of ram , this should be fine for a casual user. Heck I only have 16gb ddr4 3200 myself and I do alot on this pc.
Open up your pc and look do you have one stick of 4gb ram? (probably) then you will benefit alot from another 4gb. You might however have 2X2gb sticks because your motherboard has dual channel mode. If this is the case , both your ram slots are being used (your motherboard only has two if I found the right one) so you might not even have free slots. Because of this It might be worth selling the old stick(s) and getting some ddr3 1600 ram. This is the best ram your motherboard supports anything higher than 1600 will be throttled back down to 1600. Dual channel mode will also activate if you get two 8gb sticks.
One thing though , your motherboard is at 120°C in that screenshot. This is way to high especially if you are not doing alot on there. I would look at cleaning out fans of dust , see if any are broken and if not defiantly look at getting some better cooling going on. You will see massive improvements from just getting temperature down some parts may even bottleneck themselves to keep temperature down.
P.S I was into building computers about 12 years ago. Its a ever changing world that I have not kept up with but the guys over at
https://www.reddit.com/r/buildapc/ thrive off this stuff and will give you alot better advice than I can. This is just what I would do

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