Your activity is not illegal, you are technically the victim here if the shop sold you Pro that was cracked. You are trying to do the right thing. I've show you how to do that by several methods.
I've handled many of these cases. Most are upgraded by a shop or friend to Pro even though there's a Home license. Some even say they're sure they don't have a Home License but when they reinstall Home it activates with embedded OEM or a Digital License. So I'd wait to see for sure.
Do you need Pro? If not then I'd do the gold standard Clean install for Home, see if it activates. It's a great learning experience, because you'll learn everything that works best in Windows and how to apply it with your own hands. If it doesn't activate you can buy a key when you can afford it. Make sure to buy from a major retailer you know will back all sales, or from Microsoft directly here:
https://www.microsoft.com/en-us/p/windows-10-ho....
Deeply discounted keys are almost always bogus and will not last. There are no deep discounts in retail Windows 10.