If you want to model a hero, extract the files from the game.
I don't have the information here, "how extract", but if you search, you will find it easy.
This is the right way to make a item, because the downloadable model, sometimes have diferences of scale, or bone/ vertex names..... I had this problem with my first set.

Thanks for replying,
your reply will solve my 1st problem which is " how to import"...
the next problem is, is it possible to implement it to hero with no detail map?

With this method, you can extract all hero content.....

it sounds like you are trying to add or change a detail map for a hero, which as far as i know isn't possible, though i could be wrong. incase it isn't clear, mask 1 red controls how intensely the detail mask appears, but isn't the detail mask itself and can't modify the detail mask. i would guess the detail mask is more or less built into each hero's individual shader and can't be adjusted.
again, i could be wrong on this, but consider the conflict of having an item with a custom detail mask for a hero with its own detail mask, used on both the basemesh and possibly other items. a custom detail map for one item or set would cause problems with the base model and other items which might be equipped at the same time. even on a hero with no detail map, this would again cause problems if other people decided to make items with their own detail maps.

if anyone has a more informed answer i'd be glad to hear it, but i think you're out of luck if you're looking to actually implement a custom detail map for your workshop item. (unless, of course, you are just looking to mod your own client, in which case the possibilities are closer to endless)