Which topics should I study for IAS Exam being 9th class student???????

Well currently you are in IX Standard so here I will suggest you to just focus on following topics to study for IAS Exam

-Current events of national and international importance.
-History of India and Indian National Movement.
-Indian and World Geography-Physical, Social, Economic.
-Political System, Panchayati Raj, Public Policy, Rights Issues, etc.
-Economic and Social Development-Sustainable.
-Development, Poverty, Inclusion, Demographics, Social Sector Initiatives, etc.
-General issues on Environmental ecology, Bio-diversity and Climate Change - that do not require subject specialization and Climate Change
-Geography of India and the World.
-Indian Polity and Governance-Constitution.

for your reference here i am sharing with you the IAS syllabus please have a look on that