So, they can be hard to find information on if they are an OEM prebuilt type system. Board makers don't usually offer product pages for those type boards like they do for their aftermarket models. It's also hard to say exactly what will work in one of them because they often have very limited BIOS because they are usually fairly low end and not intended to be used with anything other than what came in them plus one or two other options so they can use the same board for several different prebuilt models.
If you are looking to only upgrade the CPU then I'd probably say it's not worth it unless you are willing to roll the dice on a used one. A new i7 for that generation, like an i7-7700 or 7700k, costs over 300 dollars while you could get a six core 8th or 9th gen Intel CPU AND motherboard for less or about that price. There are AMD offerings where you could likely get a board and CPU that are significantly better than anything you could upgrade to on that platform as well for about the same or less.
Also, your 500w EVGA power supply pretty much has to be a low quality unit because EVGA hasn't sold anything in a 500w capacity that would be considered "good" in a very long time. Too long to even consider continuing to use it IF it was one of the halfway decent 500w models they used to sell. Most likely it is a 500w B, N1 or W1 unit, none of which are good enough to consider using with any upgraded graphics card than what you have now. Both because of capacity considerations and, more importantly, because of the internal build quality of those units. They just will not hold up for very long at all and are an unnecessary risk.
I'd probably recommend doing something like this. This would give you a very significant jump from where you are now. This is, of course, assuming you have a case that supports an ATX motherboard. If you do not and must use a Small form factor, microATX or other, possibly proprietary form factor board, then a different board would need to be selected OR it might not be possible at ALL to do anything without a different case. IDK for sure, because that motherboard has no legitimate model that I can find any information on. The model you've listed is for the whole system and these OEM type systems often don't have separate board information available at all.
PCPartPicker Part List
CPU: AMD Ryzen 5 3600 3.6 GHz 6-Core Processor ($194.00 @ Amazon)
Motherboard: MSI B450 TOMAHAWK MAX ATX AM4 Motherboard ($114.99 @ Best Buy)
Video Card: Sapphire Radeon RX 580 8 GB PULSE Video Card ($174.99 @ Newegg)
Power Supply: EVGA 650 W 80+ Gold Certified Semi-modular ATX Power Supply ($74.99 @ Newegg)
Total: $558.97
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-11-09 13:56 EST-0500
Or something like this, but again, you will want to try and verify for certain what sizes/form factor of motherboard that your case supports. Posting a picture of your current motherboard IN your case, might be helpful in trying to determine that.
PCPartPicker Part List
CPU: Intel Core i5-9400F 2.9 GHz 6-Core Processor ($144.99 @ Amazon)
Motherboard: ASRock B365 Pro4 ATX LGA1151 Motherboard ($93.98 @ Newegg)
Video Card: Sapphire Radeon RX 580 8 GB PULSE Video Card ($174.99 @ Newegg)
Power Supply: EVGA 650 W 80+ Gold Certified Semi-modular ATX Power Supply ($74.99 @ Newegg)
Total: $488.95
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-11-09 14:07 EST-0500