In less than sixty years the refugees from India had become fully assimilated ----- the local community.
In less than sixty years the refugees from India had become fully assimilated ----- the local community.
Explanation
In less than sixty years the refugees from India had become fully assimilated into the local community.
ساٹھ سال سے بھی کم عرصے میں ہندوستان سے آنے والے پناہ گزین مقامی کمیونٹی میں مکمل طور پر شامل ہو چکے تھے۔
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assimilated into means to cause someone or something to be absorbed into something.
we use the "into" preposition with "assimilated" because in the above sentence "from 60 years India become fully assimilated into the community"
ND23-2-2023