Warning - lots of images!
Requirements
Instructions
Open the Mod Helper; it defaults to the SGA Extractor view (as this is the first step in getting to most of the game's assets). If you don't have your own directory for cope's SGA Extractor command-line tool (you will need to set the folder manually in this case), my Mod Helper does come packaged with it.
Then you need to set the location of any SGA archives you want to extract from. For example, the default game directory for its archives is (for my Steam install):
X:\SteamAlternative\SteamApps\common\Dawn of War III\DoW3\archives
This will then populate the dropdown with all SGA archive files found in that folder.
Select the one you want to extract, and then set the output folder (which can be anywhere you want).
You should then have a view that looks something like this one:
Once you hit "Convert selected", you can track the progress by the bar at the bottom. cc2sga.exe doesn't provide much programmatic feedback, so for the larger archives (or ones with lots of files inside) you may be waiting a while here.
At the end it should tell you how many were extracted (this line is directly from the cc2sga.exe tool).
And you're done! Do with the resulting files what you want
Complete imgur album link here.
Comments
Sound_Priest
It's not working now... Archives list not active((

Gorb
@Sound_Priest
I just tried this myself and it worked fine (extracted the Data.sga from ../engine/archives):
Did you do anything before it broke on you? Did you extract another archive first?
Sound_Priest
It's my first attempt. I copy dowModHelper_v0-6-1, cc2sga and rgdConv v1.4 in dirs on harddrive, install Java 9, my net framework is 4.7. Launch ModHelper, pick cc2sga folder, then pick DOW3 archives folder and dropdown with all SGA archive files is still innactive.
All tools downloaded from this page:

Inside .jar I not found readme file
Gorb
Going to have to install Java 9, I think.
Also, the readme should be in the ZIP, not inside the JAR. There is a JAR file inside the ZIP
Sound_Priest
Java 9 already installed. The dropbox link follow to .jar, but not .zip


Gorb
@Sound_Priest
Sorry for the delay. Here's the ZIP: https://www.dropbox.com/s/z00x741930y8i9g/dowModHelper_v0-6-1.zip?dl=0
I've just sorted out a fresh eclipse install, and Java 9. Ran the code with no issues (see attached). I recommend deleting the /conf folder and relaunching the application.
Sound_Priest
Now it works! Thanks!