Modding: Changing civ speech - Where are the source files? (for "Sicilians speaking Norman/Burgundian" mod)

My aim is to create a mod “Sicilians speaking Norman (Burgundian)” by switching the speech language of Sicilians to be using Burgundian speech (sounding more like Normans).

I am aware of the google sheet document with all the IDs, it’s just I have no idea how to use it. As I understand it, the Sicilians have codes ranging from 8600-8700. According to this guide, I am supposed to find these files and rename them accordingly (eg. 8600.wem → sivmb.wem)

However, I see no such files with these ID numbers and therefore I have no idea where to find them and how to move forward. Can anyone help?

So… I have opened empires2_x2_p1.dat file via Advanced Genie Editor and found grouped files (like sivmb.wem or mymb.wem for Mayans but for all civs) and I picked the choice → Copy source civ to target civ , saved a new dat pack under the same name (and changed the old one) but now the game won’t start. Main menu loads, but no match can be played and I’m stuck at the loading screen…

I don’t know man. The website seems pretty shady, I can’t even open it on my browser.