You can get to these files from CometChat administrative panel.
Kindly browse through the following options
Browse through the Admin panel Settings as shown below and click on editor tab.
Kindly browse through the file options on the far right top, to select which file you wish to modify. As shown below in the screenshot
NOTE: Kindly note, CometChat only allows you to modify the above three files. If you modify any other file apart from these three, you would lose the capability to update CometChat to the latest version. We strongly recommend not to modify any of the CometChat files.
If you wish to know more about "How to update CometChat?", kindly refer through the following documentation link mentioned below