The sound feminine plural (جمع المؤنث السالم) is formed by removing the taa marboota (ة) from the singular feminine form (if present) and adding the suffix ـاتٌ. For example: طالبة (female student) → طالبات (female students), معلمة (female teacher) → معلمات (female teachers).
Unlike the sound masculine plural, the sound feminine plural is used for a broader range of words. It's not limited to feminine human beings — it's also used for many masculine words that don't have standard broken plurals, certain foreign loan words, verbal nouns of derived verb forms, and some other specific categories. For example, the word اجتماع (meeting, masculine) has the sound feminine plural اجتماعات.
The case endings for the sound feminine plural have a unique feature: in the منصوب (accusative) case, it takes a كسرة (kasra) instead of the usual فتحة (fat-ha). So you get: طالباتٌ (nominative, with damma), طالباتٍ (genitive, with kasra), and طالباتٍ (accusative, also with kasra). This is one of the few places in Arabic where the accusative and genitive case markers are identical.
When forming the sound feminine plural, be careful with words whose taa marboota was preceded by a long vowel. Words like حياة (life) become حياوات (with the taa marboota reverting to its original root letter و). These special cases are covered systematically in the Sarf courses on Ilm Al Lughah, with flashcard drills to help you internalize the patterns.