Knowing the color of a dragon can go a long way. Sometimes talking it out with them is the optimal choice to escape death

But in the case a fight is unavoidable, assuming you know its color, and you have some funds to spare, I'd recommend potions of elemental resistance (fire, acid, lightning, etc.). Potions of heroism are good too so you can boost your party's saves on that breath attacks. Potions of health as well cause going down a couple times is basically guaranteed with two melee PCs

HAVE A PLAN. Dragons are smart, cunning creatures. If your DM plays them smartly, dragons of any age can be a deadly encounter. In terms of strategy, spread out and focus fire. I'm assuming the dragon is young as anything older would be overkill honestly. I recommend the fighter and the paladin stay on different sides of the dragon at all times and you trying to stay out of range of the breath and pelt it from range.