Hi @Mred3car, how are you today?
If you were charged for Dropbox, then most likely you do have an account. Since you're posting on the forum, you should already be signed into it.
You can check which account you're using by visiting this page.
In addition, if you've recently been sent any emails from Dropbox, you'll be able to see the full email address there.
Keep me updated with any progress!