Nevermind, I figured it out.
Here is how I did it.
Install an application like universal extractor for windows. Using it you can decompress the tar.md5 file.
It is basically a tar compressed file so any tar extractor should work.
But my work was only half done, I found the file modem.bin but I did not have a way to flash it to the phone. So this is the workaround I made:
I decompressed another CWM flashable modem zip file, replaced the modem.bin of that with the new modem.bin extracted from the firmware package and then rezipped all the files.
Flashed it via CWM recovery and it worked like a charm

Managed to update my modem.