Did you pay by credit card, you should be able to pull up old statements online to get dates and the ops name.
Did you use a digital camera on those trips, providing you set the camera up right it records date and time for each picture, okay for those locations you’ll need to figure out the time zone which is one of the reasons mine is set for a 24 hour clock.
The dive log is a journal of your adventures, I would make pages for those dives and fill in what you remember.