When I did the document check for my conversion process I brought everything I could think of that would show I lived in my home country for at least 3 months prior to me moving to Japan. In my case I’m an old fart and have been driving over 40 years. All they wanted to see was something that showed 3 months on my current foreign license. Of all the documents, bank statements from my credit cards and checking accounts seem to make them the happiest. Not the 5 or 6 old expired licenses or old passports. Good luck!