Kobo is best for epubs format. Use Calibre with tools from "Apprentice Alf" to convert. It appears that Kobo readers can read mobi format but with mixed results (I've never tried it myself). The firmware is the same as on the other Kobo models (Touch & Glo).
This thread gives you more details, post #4 in particular.
https://www.mobileread.com/forums/sho...ight=Kobo+mini