A **CBASIC** to QBasic convertor is probably possible to do. But unless someone has one already written somewhere you have your work cut out for you.
( POSSIBLE <> EASY/PRACTICAL ) I always like to make that clear !
If you have more CBASIC code you want to convert then it might be worth writing a convertor. You'll need an indepth knowledge of both BASIC syntax's to do that !.
If this is the only thing you need to convert then a manual file by file conversion will probably be a little quicker than writing a general purpose convertor. Again you will need knowledge of BOTH syntax's !
I tried building cbasic but no luck, you probably need a distro from 12 years ago, I don't know if I have a VM that old with all the needed tools/utilities