Magic stone and thrown weapon fighting dd 5e tashas

I am a ranger with multiattack and thrown weapon fighting. I have a sack (homebrew) that lets me draw and throw a magic stone (flavoured as a turnip). I think i have established that i would have three attacks (multiattack and bonus) . thrown weapon fighting lets me draw as part of the attack. my question is . do i add the usual 1d6+wisdom modifier damage on the offhand throw? or is it just 1d6? the cantrip is cast on the stone. im unsure. essentially , if someone throws the stone with the offhand does it still hit with the modifier damage?