All error, warning and advisory messages have a unique number which is typically displayed at the start of the message. For example:
example.c: 5: (751) arithmetic overflow in constant expression (warning)
The unique message number here is 751. All messages are documented in the "Error and Warning Messages" chapter of the user manual.
If you are compiling in MPLAB® X IDE, double-clicking on the error message will highlight the line of code, causing the error.