[{"rows":[["123","234","345"],["345","456","567"]]},{"rows":[["111","222","333"],["444","555","345"]]}]

db.collection.aggregate([{"$unwind":{path:"$rows",includeArrayIndex:"row_i"}},{"$set":{"col_i":{"$indexOfArray":["$rows","345"]}}},{$match:{"col_i":{$ne:-1}}},{"$project":{"value":"345","row_i":1,"col_i":1}}])