necesito saber cual de estas formas es correctas
We eat orange. or We eat an orange. thank you.
We eat an orange is correct.
If you said "We eat orange" your audience would be expecting something orange to be an adjective, followed by something else. For instance, "We eat orange cake".
Maybe you got the idea for the question from Paralee's lessons. For example "She eats a strawberry." But "She eats Pizza." and not "She eats a Pizza." So why not "she eats strawberry / orange" ? The reason is that it is normal to eat a whole strawberry or orange but it is not normal for someone to eat a whole pizza. So we have to drop the article "a" which indicates a whole pizza but we do not drop it when we are talking about a small thing like an orange. If we do it sounds strange.