Two days ago my friend Tom found me, I did not know about that until one day ago. NOW, I am writing an email.
Which one would be used correctly in my email?
I know that Tom found me
I knew that Tom found me
If Tom found you two days ago, then it's difficult to see how you did not know about it at the time. If you mean that he found you on Facebook, or found your address, then you need to make that clear. If he found you in one of these ways, then you know now that he found you.
Thanks for your suggestion.