I appreciate what you are trying to do, re-purposing an office machine on a budget.
Lots of if's n but's but here goes ....
I THINK this is the mobo manual ....
https://www.manualslib.com/manual/437051/Hp-Z210.html?page=15#manual
It looks like you have a PCI-e 16x slot available ...
It looks like the small format graphics card you have chosen will fit inside the case you will be buying.
BUT - be mindful that the powersupply youll get might NOT have the power plugs for a graphics card abd may not have enough WATTAGE. It also may not be easy to swap the power supply for another. Once upon a time I think I recall "office" type machine builders using non-standard connector types between PSU and motherboard.
Assuming you overcome all these potential issues the PC you will have (on quick analysis) will be a quite low end affair.
May I direct you to this thread. I know it is a few years old but might give you an idea on how to do better for your money. You have 325 for the HP system in mind and 200 more for the graphics card - see what the guy in thread did for 500 dollars ...
https://pcpartpicker.com/forums/topic/74438-a-500-canadian-budget-gaming-pc-opinions-please
Good luck!