Hunter's Mark with Multi-Damage Spells

Hunter's Mark says it will "deal an extra 1d6 Force damage to the target whenever you hit it with an attack roll." Which I read as it can be added to spell attacks damage. So when you have a spell like Ice Knife that deals 1d10 on a hit then 2d6 to everyone in an area, hit or miss. Would I add the HM damage to the 1d10 AND the 2d6? What if I miss the target? The 2d6 still does damage. I'd precieve that as an automatic hit, even if the original attack misses. Would I be able to add the HM to that? And what if my quarry isn't the target of the original attack but is in the area of the 2nd hit? Does any of the calculations change?

The spell Hunter’s Mark effectively let you deal an extra 1d6 Force damage to the target whenever you hit it with an attack roll made with a weapon or a spell.

Only the creature you magically mark take this damage if you hit it with Ice Knife , meaning it will not if you miss, nor does it apply to the 2d6 Cold damage resulting from a failed Dexterity saving throw.