Whenever you want to use C programming language to do something, you first need to learn C programming. This forum is not for teaching you the C programming language. Since you use BASIC for PIC (Peripheral Interface Controller), it wouldn't be difficult for you to use C for the same purpose. However, there is lot of difference between BASIC and C.
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"All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)
If you download the Microchip IDE you can get some free and trial version C compilers, and your programs will run in the included MPLAB SIM simulator.
There are some parts of C that just don't translate well to the PIC processor, but those are usually advanced topics.
There's also some functionality that was built into the BASIC that you used (built in functions) which probably won't be present in the C library, so you will have to be more intimately familiar with the hardware registers and some assembly language.
Also your best bet would be to target the PIC18 or higher processors, if that's an option.