Basically, you aren't going to find "the solution" that fits your exact application and your exact code: it doesn't exist. That's the case for most applications, for most code.
We can't point you at code you can just drop into your site and it'll do what you want - you need to look at the solutions you have found (or some of these: Website send order confirmation email C# - Google Search
]) and work out how they do it. Then you can adapt that approach (or at least the "send an email" bit) to your circumstances and needs.
Sorry, but we can't do that for you!