If you haven’t already, create a AVR C project. Open the properties of the project. Under C/C++ Build, select Environment, look for the PATH variable. It should have an entry that reads like
<ide root folder>\plugins\com.atmel.avr.toolchains.win32.x86_184.108.40.206009140852\os\win32\x86\bin. That is the folder containing all the toolchain binaries including avr32-objcopy.exe.