Both .el5 and .el6 files come from a tool called Easy-PhotoPrint EX from Canon, but due to the difference of sue of both formats el5 to el6 conversion is actually not likely, unless the .el5 layout file can be exported to .el6 files directly.
What is more likely is that EL5 to EL6 conversion is related to Enterprise Linux 5 and Enterprise Linux 6 and not actually to any file conversion.
Updated: October 11, 2023