I'm pretty sure he means the secure_file_id

I have no idea how to get them, but I know the one of Borderlands 2, because it came with the description of the "using pfdtool without cfw" method to decrypt saves and use them with the Borderlands 2 save editor. It is 02010508040102010508030A0F070C0D. I searched for hours, couldn't find any for other games though :/