Where to Track child green card status

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HI senir members,

me and my wife got our GC while we are in india. we entered in usa june 2011 alog with 18moths kid. on port of entry immigration officer issued 1 year immigrat visa to my child and he said my child can get green card with in a 6 moths. till we are not received my chold green card. so where shoud i track my child green card status. plz reply me thanx in advance

regards,
Gous