What specifications or requirements does our Ada code need to meet to be used by Ada-C/C++ Changer?

It must be self-contained and compilable by an Ada 95 or Ada 83 compiler. If you use third-party libraries which are not part of the Ada standard library, you will need to at least include the Ada source code for the package specs for such a library. If you want a translation of the third-party libraries as well, you will need to include the Ada source code for the package bodies of the library as well.