You need to set up your account as IMAP in order to be able to see the Sent folder.

Thank you for the response. Can I switch my account to an IMAP setting after being set up as something else? I uninstalled Thunderbird and re-installed it but everything comes back up as it was. I don't get prompted to set up the account again.

You can't switch an existing account. See http://kb.mozillazine.org/Convert_a_POP_account_to_a_IMAP_account

I uninstalled Thunderbird and re-installed it but everything comes back up as it was.

You're wasting your time. The profile data is separated from the program installation.

OK... I tried following the instructions, but I'm having trouble setting up the new account. Is there a phone number that I can call for Support? Or is there any way to delete everything and start over from scratch?

Is there a phone number that I can call for Support?

As there are no costs involved in using Thunderbird, there are no monies for paying people to sit on the end of a computer/phone etc. The people answering questions here are mostly volunteers dedicating their time to help other users.

I tried following the instructions, but I'm having trouble setting up the new account.

You'd need to explain in detail what you did and where you got stuck.

Or is there any way to delete everything and start over from scratch?

There certainly is.

I would like to delete and start over. Can you direct me on how to accomplish this?

If you start over you'd still have to set up the IMAP account. Since you were saying you're having difficulties setting up the account, you'd possibly run into the same thing again when starting over. So I'm not sure what exactly you think you gain from doing so.