MPLAB help menu has old pdf's in the C32 compiler section – don't use! In the general section there is the proper help file links which is the current documentation
You may have two MPLAB C32 directories:
C:\Program Files (x86)\Microchip\MPLAB C32 Suite\
The compiler that is installed from MPLAB IDE's installer.
C:\Program Files (x86)\Microchip\MPLAB C32\
The MPLAB C Compiler for PIC32 MCUs standalone installer.
Main uC file – all register names, bit names etc:
C:\Program Files (x86)\microchip\MPLAB C32 Suite\pic32-libs\include\proc\
Names used in libraries etc
C:\Program Files (x86)\microchip\MPLAB C32 Suite\pic32-libs\include\peripheral\