The SSDI and GAS files did not come with version 3.0. If you want them you have to find them on one of your old 2.x versions that had the "SSDI" and "Gazetteers" on the disk. If you want to use them you have to run the program and insert the old 2.x disk in order to get the data. The Gateway fot them program was not provided on 3.0 either but you can create a shortcut directly to them if you desire.
If you do not know what they are you probablt do not need them anymore.