As I said in the question header, how can I read or access the source codes of exploits in Metasploit on Kali?
Note: Please, don't say "did you look under ~/.msf4". Because there is no anything except empty folders.
I'm pretty sure ~/.msf4 should only mainly contain user custom settings, as it usually is for hidden folders under the Linux user home directory.
The framework files are in the following folder:
/usr/share/metasploit-framework/
I don't know which version you're using, just type this to find it:
cd /usr/share/metasploit*