Inside the Ninteno 3DS folder there will be another folder that is named a bunch of random hex characters. Inside that folder there will be another folder that looks similar. In the second folder there may or may not be a folder called "dbs." Inside the "dbs" folder there should be two files called "title.db" and "import.db." If those are there, that's not the issue. If they aren't there, you need to create them. If the "dbs" folder isn't there, you'll need to create it in Nintendo 3DS\<hex characters 1>\<hex characters 2>\ (the directory will look like Nintendo 3DS\<hex characters 1>\<hex characters 2>\dbs when you're done). Inside the "dbs" folder, create two text files; the names don't matter. Rename the text files, including their extensions, to "title.db" and "import.db" and reinsert your SD card into your 3DS. Go to System Settings > Data Management > 3DS > Software. Allow it to repair the database. After that, you're done.
