"______ cant be downloaded due to missing sd card"

So I rooted, unlocked bootloader, flash custom recovery, flashed custom kearnel/rom, and somewhere in that process i unmounted or erased or something idk my internal sdcard.... Google and I have been looking for the latter part of the day for a fix or answer till I finally had to break down and open a thread. please can someone point me in the direction or instruct me on how to reformat or repartition my phone to have storage without flashing factory firmware? im also unable to mount my external sdcard aswell. Im running a 6.0 mm rom with missing storage.

Thanks,
DirtyWhiteBoy707