It says I have achieved 2/3 of this mission , which I must have done accidentally,  but I cannot find the champion in question and I have equipped several more with the required artifacts but to no avail.  I am unable to complete this mission at all.  Some advise would be appreciated

i

Go to your artifacts, filter them so that only Gauntlets, Chestplates and Boots show, select ATK(%) primary stats to show only, then choose the filter option to show equipped items too.

You will see little images of the champions who have the items in question equipped.

Seeing you are in quite an early stage of the missions, you may not have a hundred champions with such items equipped already.

I hope this helps.

Okay first of all make sure your hero is an ATTACK type

Signified by the ATTACK designation on the top right of the hero

i

Second, make sure you equip the right equipment, as the task required only GAUNTLET, CHESTPLATE, and BOOTS hae an ATTACK% primary stat. The primary stat of any equipment is the top one and is the one that is written in bold

i

Make sure the stat in question is in percentage, because theres also the flat number ATTACK primary stat.

I hope that 

lee.oz0213 - That's why I'm confused, on the surface it appears I have done exactly that, hence the confusion but thanks for the reply, it's appreciated to have the answer re-enforced.

watchdogCZ - that's interesting, I wasn't aware of these filter functions, I'll give that a crack. 

Cheers to you both for the support.

oh one more thing that i seem to be missing, you have to equip EACH hero with 3 artifacts (gauntlets, chesplate AND boots) that have the ATT% primary 

The mission only required to equip 1 champion with those 3 ATK% artifacts.