So, a lot of people on ebay do not post what firmware a 3DS is on, either because they can't and the top screen is broken, or just because they didn't, which for some reason annoys me. Anyway, starting the guide now. If the 3DS home menu looks like this , with the house and wrench, it is above 9.0.0. If it has no house and wrench and has miiverse, like this, it is somewhere between 8.1.0 and 7.0.0. If it does not have folder creation, it is under 4.0.0, if it doesn't have a camera it is under 3.0.0, and for some reason if it doesn't have eshop or internet browser, it is under 2.0.0 I hope this helps somone, and if I missed something or have something wrong please tell me.