What file type are they?

It says file type is NET

I am puzzled. I don't know how you have got messages onto an ftp server, and I don't know what NET means.

Ftp servers do not convert files from one format to another, nor do they normally oblige you to convert them yourself.

So something has happened that you are not telling us about, or are not able to tell us about.

Thunderbird's native storage mode for messages are mbox files, such as Inbox, Sent, Junk, Trash. Note that they don't have extensions and this might be confusing a file browser that expects to identify the filestore from the extension. This means that "NET" might be a red herring.

Basically I am switching website/email hosting from one company to another. I downloaded the mail files on to our hard drive and then loaded them on to the new server once the switch was made. Anything that we had in thunderbird was backed up on the server as well as a local folder. (I realize now that I should have said I used FTP to transfer from the server to our hard drive in my original question) I am able to open the files (that I downloaded through FileZilla in my initial step in the process) and read all of the email info in notepad but I am unable to tell you file type as I can not locate that. I thought that the type was what was populated under "type:" when hovering over each document. Can you tell I'm a newbie :)

When I set up email through our new website/email hosting company, I configured those email addresses in thunderbird and just did a drag and drop to the new accounts. Although, some emails did not make the transfer.

So now I have the missing emails in a "Mail" folder on the hard drive and just need to figure out how to get them to show up in thunderbird.

Type refers to the extension eg: .doc, .eml, .jpg etc Maybe your computer is not set up to show the extensions.

If windows OS open a folder (not in thunderbird) eg: 'Documents' or 'Control Panel' 'Organize' > 'Folder Options' > 'View' tab or 'Tools' > 'Folder Options' > 'View' tab uncheck 'hide extensions for known file types' click on OK.