"C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude -CC:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM3 -b39600 -D -Uflash:w:C:\Users\AppData\Local\Temp\arduino_build_325512/Blink.ino.hex:i
avrdude: Version 6.3, compiled on Jan 17 2017 at 12:00:53
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch
System wide configuration file is "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"
Using Port : COM3
Using Programmer : arduino
Overriding Baud Rate : 57600
avrdude: serial_baud_lookup(): Using non-standard baud rate: 39600avrdude: stk500_recv(): programmer is not responding"
Why are you running this at baud rate: 39600? -v -patmega328p -carduino -PCOM3 -b39600?
If you have a boot loaded Pro Mini, it should be 57600 Baud Rate.