Archived emails have disappeared from Thunderbird

See them in file explorer where exactly?

Archives are normally MBOX files, so there is only one file per folder of emails. That makes it difficult to "see them" in file explorer as there is only the folder name displayed. Hence more information please.

Hello Mark. Thank you for your reply to my problem. last night when I opened Thunderbird there was a message that a new version of Thunderbird has been installed and my email accounts are no longer compatible and I need to re-install them. I have done that but none of the folders I had before are there now. There is a folder in desktop called Archive pop3.optusnet.com.au - Shortcut. I could see my Archive folders in there before but they are not there now.