when you talk about wearing robe(as in clothing), do we need an s at the end of robe
for one robe it is: he/she was wearing a robe
for more than on robes: wearing robes
Right. So your question should have been "when you talk about wearing robes..."
When referring to a single robe, you generally do not need to add an "s" at the end of "robe." The word "robe" is considered a singular noun, meaning it refers to just one item of clothing. For example, you might say, "I am wearing a robe."
However, if you are talking about multiple robes, such as referring to a group of people each wearing their own robe, then you would use the plural form of the word "robe" and add an "s" at the end. For instance, you could say, "They are all wearing robes."
In summary, if you are talking about one robe, simply use the word "robe." If you are talking about more than one robe, add an "s" to make it plural as "robes."