There is no way unless there is a liaison with the next word starting with a vowel. However, you can tell if it is "femme" or "femmes" by context. Here, it can't be "femme": "Les grandes jupes des femme" is not grammatically correct. To use the single "femme", you'd have to change the preposition/article combination:
Les grandes jupes de la femme
Les grandes jupes d'une femme
So, to clarify, If I were in a department store looking for large skirts for women (let's assume here that there are men's skirts for a moment) I would have to ask for les jupes de grosses femmes and not as I would in English assume that both large and women's could modify skirts
Be aware that "grosses femmes" means "fat women".
In French, a noun cannot be used as an adjective by placing it before another noun.
Therefore, "femmes" cannot be an adjective.
By the way "les grandes jupes des femmes" is possessive: these skirts belong to the women = the women's big/large skirts.
In a department store, you could see "pantalons pour femmes", for instance, with the meaning of "women pants".
This actually isn't correct. Grammatically, adjectives come before possessives, even though this creates ambiguity about who is big between the skirts and the women. In this grammatical construction, English does not provide a way of telling whether the women are big or the skirts. This is a quirk of the English language, but "the women's big skirts" is grammatically incorrect English, and if it's being used in the French to English Duolingo course (which I assume it is) then it's teaching French people incorrect English.
Buildings are tall. People are tall. Some clothes are labelled tall so they can be categorized for use.
But the clothes themselves, in their natural state when not being held up by people or racks, are not tall. In fact, they are quite short, usually no more than an inch or so in height. Some unusual designs might go as high as three or four inches.
There are rules regarding adjective placement with respect to the noun if modifies. You will note that it is grandes jupes with the adjective in front. With the adjective in front you can take it to mean an inherent quality of the noun. Some skirts have the inherent quality of being long but they are not tall. If it was classified as tall, as in size tall, you would see the adjective after the noun. jupes grandes
It could be that the French do not apply the customary adjective placement rules when it comes to clothing but it does seem like Duo is applying the rule here.
Indeed you must use a "de" to make a possessive in French. I suppose what you suggested comes from the English structure "the women's skirts".
That type of structure is rather Germanic, you have it in Dutch as well for instance. And precisely in Dutch/Flemish, there is a rather colloquial but still correct similar structure: "de vrouwen hun rokken", literally "the women their skirts".
And well, you sometimes find that in French too, especially in Belgium : "les femmes leurs jupes". But in French, that is a mistake and even if you can hear that regularly, it will rather be to emphasize, highlight the possessor.
Example with literal translation: "Les filles, leur vestiaire est de l'autre côté" = "The girls, their changing room is on the other side". "Les ouvriers ont moins de libertés. Les employés, leur statut est différent" = "Labourers have fewer liberties. Employees, their status is different.
So in this exercise, you could say "Les femmes, leurs grandes jupes (doivent être rangées là-bas)", but then you need at least the possessive determiner, here "leurs" (=their). But you must remember the correct, regular structure with "de".
I think any dictionary could give it to you, but basically "grand" is "big, tall, large, spacious" whereas "gros" is rather "big, fat, thick" - especially for people.
And here, you can't say "Une grosse jupe" if you talk about its size, its length ; now if you talked about the thickness of its fabric, maybe you could say "une grosse jupe".
Let's take "a tree" : if you say "un grand arbre" it rathers means it's a tall tree ; "un gros arbre" would rather mean it's a wide, large tree.
Sometimes you can use one or the other, in a figurative way :
- I have a big problem = J'ai un grand / gros problème.
Duo often tries to discourage users from copying the French syntax when a different syntax is much more common in English. We can say it either way in English, but French can only say it the one way. Duo, therefore, it trying to build a strong mental link between the most common English syntax and the correct French syntax.