If you mean Dragon's Archers/Archers of the Dragon it would be "Dracōnis sagittāriī"

Or if you mean Dragons' Archers/Archers of the Dragons it would be "Dracōnum sagittāriī".

As an alternative, it could be just "Dracōnēs sagittāriī", dragon-archers or archer-dragons.

Note: both terms of any of those three sentences may be used in whichever order you like.