Although the OS/VS COBOL compiler is no longer supported, the programs that were generated by it are supported if they are running under Language Environment. Once you have moved your run time to Language Environment, you can run your source code through a source conversion tool, such as the COBOL and CICS Conversion Aid (CCCA) and then compile using the Enterprise COBOL compiler.
For more information on CCCA, see Conversion tools for source programs.