Hi,
Version 2.50 is almost 10 years old now. The 16F18313 is new device and according to the version history preliminary support for it was added in the latest version of PBP (3.0.8).

I don't know the details about that device, and/or if it's possible to create your own device specific include file for it and compile using 2.50 or if relies on low level library functions and/or internal compiler support added since 2.50 but if it was me, and I really had to use that device I'd strongly consider upgrading.

I haven't checked but the PICkit3 "should" be able to program the device.

/Henrik.