I understand that you want to convert the set of C/C++ code that you gave links to PowerBasic/GWBasic, but why do you want to convert it to basic?

There are other ways you can utilize this various programs as standalone ones that you will be able to take their output and input it into your own program without the need to actually converting them to BASIC.

One of the links you gave (this one) is a very straightforward tutorial that uses very simple C code that you can easily learn (especially if you are already a seasoned PowerBasic programmer) and implement it directly in PowerBasic.