Please do not interfere __________ my personal affairs.

Please do not interfere __________ my personal affairs.

Explanation

Please do no interfere in my personal affairs. 

براہ کرم میرے ذاتی معاملات میں مداخلت نہ کریں۔

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Interfere in means مداخلت کرنا: When interfere is followed by in, it means to get involved in something that doesn't concern you

"In" is used as a proposition here