The motherboard in your computer is HP proprietary. It has a 4-pin power connector instead of a standard 24-pin ATX power connector. You will have to buy any PSU upgrade from HP. HP has a 500W PSU (L05757-800). However, it doesn't appear that they have it available in your country. Here it is in HP PartSurfer: https://partsurfer.hp.com/Search.aspx?searchText=L05757-800
You should contact HP Customer Support to see if they can sell you one.
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