when i place order i get this error how can i handle it

After clicking on Place Order i get this error…

{“message”:”Order validation failed: orderItems.0.product: Cast to ObjectId failed for value \”3\” (type string) at path \”product\” because of \”BSONTypeError\”, orderItems.0._id: Cast to ObjectId failed for value \”3\” (type string) at path \”_id\” because of \”BSONTypeError\””}