How we can does masive change of sintax to searchs queries relative to upgrade saplunk version from 6.4 to 6.5 and finnaly 7.3?

Hello, we are planning to upgrade our splunk platform from version 6.4 to version 7.3. We implemented a server with version 7.3 and detected a change in the syntax of our search queries. we want to know if there is any mechanism to change the syntax automatically thanks