Buy Guilmon mercenary eggs, or hunt for them, by killing a lot of those monsters:
Guilmon Snowstorm Village Levels: 31-34
Guilmon Frozen Ground Levels: 40-42
Growlmon and Wargrowlmon can also be summonned with their Boss cards and sometimes monster cards lv2 or 3.
Then you'll need a lot of dragon datas, you get them by scanning data magic eggs (scan cost: 125bytes).
After that simply use the incubator with those items in bag.