Learn Spanish (Latin America): Queremos comprar esas faldas largas hoy.

The word esas means "those" and it must match the noun it describes in both gender and number. Since faldas (skirts) is a feminine plural noun, we use the feminine plural form esas. If we were talking about masculine items like pantalones (pants), we would use esos pantalones.

Why is comprar not conjugated like queremos is?

When two verbs are used together to express a single idea, like "want to buy", only the first verb is changed (conjugated) to show who is doing the action. Queremos changes to match "we", while the second verb, comprar, stays in its basic dictionary form (the infinitive) meaning "to buy".

Does largas mean "large"?

No, largas is a classic false friend! It actually means "long". If you want to say "large" or "big", you should use grandes. Notice that largas comes right after the noun it describes and ends in -as to perfectly match the feminine plural faldas.

Where is the Spanish word for "we" in this sentence?

The word for "we" is nosotros, but Spanish speakers usually leave it out when the context is clear. Because the verb queremos ends in -emos, it can only possibly mean "we want". The "we" is already built into the verb, making the extra pronoun unnecessary.