Assuming you did not buy from the Mac App Store, your MacGourmet Deluxe 4 database is a file named MacGourmet4Database.mgdatabase, and is located in Documents, if you use the default location, or in the location you choose to create it the first time you ran the application. You can also always find this file by selecting the "Where is My Database?" menu item from the Help menu within MacGourmet or MacGourmet Deluxe. This will open the folder containing your database.
To backup your recipes, copy this database file to a thumb drive so that it's off your Mac (in case of system faiure).
If you are using any Mac App Store apps they all store their data in the "Containers" folder. You can still find it by going through the Help menu function listed above, or, manually, via this location:
is in your user's home folder, that is what the ~ denotes.
So It might be something like <name of computer>/<Name of Hard Drive>/Users/<Your User Name>/Library/Containers/