Does it not have a sticker on it ,probably on the back which will have the model name/number.
What is your budget for the graphics card as the one you have chosen would not be my first choice.Though it will work in your PC.
Despite what you have said about the PC being new, I have to assume that you bought it Second Hand as, had you bought it new, you would have lots of pieces of paper telling you what Model you had bought.
Download this Belarc and it will tell you what you have inside. Then you can pass the details on to us. From memory, Zoostorm was bought by Dell a couple of years back and is used, by them, to brand their Gaming Computers. So you should have a pretty capable machine of whatever vintage
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