I have source code written in C. I want to convert it
into C++. I have tried to manually do but it will
consumes a big time and effort.

Yesterday I found the converter which convert from C
to C++. It is written in Python. I have problem when I
run it.

Could somebody help me ?

What exactly do you need this for? A lot of C code can be compiled with
a C++ compiler after spending a few hours with it. There are weird
differences but, assuming you don't have a lot of "clever tricks", it
should be a relatively straight-forward process.