Upgrading from v3.x to v4 is fairly simple. Below are the major changes that are released as a part of CometChat v4:Please follow the setup instructions to upgrade to the latest V4 version.
In v3 the import class package name start from com.cometchat.pro.* . Change it to com.cometchat.chat.* everywhere in the project and you are done with v3 to v4 migration