There are many BASIC compilers for the PIC range of microcontrollers. You'd have to be more specific to which one is needed. The syntax changes between them so if you've got a prewritten program you'll need to find out which one it wants.
Most PIC compilers however are commercial and you'll need to purchase it.
L.E.T. PIC BASIC Lite is free but you'll need to buy it if you want to use the built in support for serial, LCDs, I2C etc.. you'll need to buy the full version. I've not used it personally but it's the first thing that came up in Google.
- Trevor