you have a Pavillion 500a6? That's from 2013? In computer terms, that's pretty old. According to the specs https://support.hp.com/ie-en/document/c03786042 you have a 100Mbps ethernet adapter.
Why can't you add a gigabit ethernet port? It's 5 years old so warranty is long gone, and it's a desktop, so it is made to be extended.
If you have a recent smartphone or tablet, there's a good chance it's faster than your PC in all aspects, and you can just run the test from that. If your ISP says you get 200MBps that means their modem probable has WiFi to support that.