It's simple. Go to Tachiyomi and create a backup. Then, in Mihon, during the first setup, it should give an option to restore backup. You can also resotre backup in Mihon settings, then go to extensions and (trust) the restored extensions.
It's pretty much the same app at its core. So no need to change file names or formats. Everything should transfer.
Great! Now I can add more fast storage to my Samsung Phone that I bought during the past 4 years...oh wait