The patrol logs that SH3 Commander generates are in Documents\Personnel Files\SH3\CommanderName. Once they are made you should find Log_#.html files. Similarly personal file, crew list and tonnage ranking are in HTML. But if you don't have one then I guess you have to create a fake campaign and fake patrols, make logs for it and edit them with the data of your older campaign. (Sorry, repeat of what BlackSwan wrote)
There was an update at some point. This is the latest version (1.2) of the log editor.
https://www.subsim.com/radioroom/dow...o=file&id=4530
I vaguely remember JScones writing here about a way to import entries from a text file. But you'll have to search for details on that.
P.S. Backups, backups, backups, backups, backups, backups, backups!