this tool which will replace weapon/vehicle/class names in your Alpha made missions to work in Beta.
Quote Dingo-J :
This small application will read .sqm mission files made in the Alpha version of Arma 3, look for and replace names for vehicles, classes, and weapons that changed in the Beta release of Arma 3. Changes are made using the supplied ChangeText.txt file. This will only convert .sqm mission files.