Please try the following ...
First, to be on the safe side, make backups of your host data, and backup your entire /Library/application support/appsolute/MAMP PRO/db/ folder.
To verify this is your old database data, look inside of this mysql56 folder, you should see subdirectories of all of your old databases in this folder.
If you see missing databases in MAMP PRO 5, you can "reupgrade" your old data by doing the following.
1. Quit MAMP PRO
2. Rename your mysql57 folder to mysql57_back
3. Make a copy of your mysql56 folder, name it mysql57.
4. Start MAMP PRO, start your servers
5. Run Tools > Upgrade MySQL DB