Oh dear. The bad news is that msf files aren't really of any use to you. They are used to manage the display of the messages which are actually held in mailbox files. So, for instance, Inbox.msf refers to a data file named Inbox - note that it doesn't have the usual filename extension. The standard guidance would be to copy the entire profile, which in addition to your messages, also would preserve all your account settings plus address book, filters, customizations and add-ons. If you have reformatted then it may be too late to recover your data. Unless the affected accounts used IMAP, in which case the data should still be on your provider's server. Just set the accounts up again in Thunderbird.