For all of the new people starting out with the MiSTer project that want to play some Neo Geo games. The format that your legally attained ROMs need to be in is the .NEO format. If you're like me and had a hard time figuring out how to get your legally attained ROMs in that format I'm here to help.
Months after I had already had a collection of ROMs in the correct format I was looking into buying a Neo Geo and a flash cart for it. That's when I came across the Stone Aged Gamer site that had a link to a program you are supposed to use to convert your Neo Geo ROMs into the .NEO format. If I had known about this program when I first got my MiSTer I would not have spent hours searching for the correct format.
The program you need is called NEOBuilder. It can currently be found at https://stoneagegamer.com/neosd-downloa ... neobuilder
If you have any desire to play Neo Geo games on your MiSTer and want to convert your ROMs to the correct .NEO format I would download it ASAP. These flash carts haven't been in stock for years and there is no telling when that web page will be taken away, along with the download link.