Hi I would like to ask if the corsair cv450 psu will work with my ryzen 5 4650g PRO and my gigabyte a520m s2h motherboard
As far as the amount of Wattage needed to run the Ryzen 5 4650 Pro the Corsair CV450 has plenty of power to run your Desktop PC with that APU processor without a separate GPU card installed.
But if you should decided to install a GPU Card in the future then depending on the GPU card you install the CV450 Watt PSU may not be strong enough.
"You need a power supply with at least 300W"
https://www.whatpsu.com/psu/cpu/AMD-Ryzen-PRO-4650G/
300W is the bare minimum. 450W will do the trick.