sure.
1. decrypt and extract the .cia to somewhere on your PC
2. in the folder where you extracted the .cia, go to "RomFS" > "rom"
3. rename the file found in the rom folder and rename it "foo.gb/gbc" (.gb for a gameboy rom, .gbc for a gameboy color rom; replace foo with a name of your liking)
4. copy the file to a safe place on your PC and run it in an emulator
again, i did this with a pokemon crystal .cia, but this should apply to any gameboy/gameboy color game.
you can decrypt/extract 3DS roms with quite a few tools. i decrypted the .cia and turned it into a .cci with
Batch CIA 3DS Decryptor and then extracted the decrypted .cci with
.Net 3DS Toolkit.
another handy way to access the contents of the .cia on PC is using
ninfs and following the steps i described in
my previous post. this bypasses the need for decrypting the .cia, but you will need your boot9.bin file and a seeddb.bin or a seed for the game you're mounting.
- you can dump your boot9.bin using GodMode9 and you can dump your seeddb.bin using GodMode9 and SEEDconv. instructions for the seeddb.bin are in the github repo readme. just know that you can't mount the .cia if your seeddb.bin doesn't contain the seed of the game you're trying to mount, that is if the game is not/was not installed on the 3DS you dumped the seeddb.bin from.