There are major differences between Basic and C. As a starting point, I would read an online tutorial on C so you can see the syntax differences. Also, C has no intrinsic I/O functions like Basic. They are all part of the Standard C library. If you read a tutorial, you will see how important libraries are to C, where they almost don't exist in many dialects of Basic.
As to which tutorial to select, that's a matter of personal preference, plus I'm a little biased. Google "C tutorial" and read a little and, if you don't like what you read, try another until you find one that makes sense to you. After you complete the tutorial, chances are you won't even need to come back here with your question.