Many nouns and pronouns in Urdu change if they are followed by a postposition. This is true for both singular and plural nouns. We say that any noun or pronoun followed by a postposition is in the oblique case. How do the nouns change? The simplest formula to remember is: For singular nouns: the masculine noun ending ا (ALIF) changes into ے ; all other masculine nouns don't change, and feminine nouns don't change. For plural nouns : all oblique plural nouns end in وں Here is the formula in more detail:

Oblique examples with the postpositionمیں (in)

Plural	Singular
سنتروں میں	سنترے میں	Masculine nouns: Type 1 Ending in ا
پھلوں میں	پھل میں	Masculine nouns: Type 2 Not ending in ا (all the rest)
روٹیوں میں	روٹی میں	Feminine nouns: Type 1 Ending inی
دوکانوں میں	دوکان میں	Feminine nouns: Type 2 Not ending inی(all the rest)