Чтобы преобразовать прямую речь в косвенную, нужно сделать следующие изменения:
Исходное предложение: "The kids played tennis in the yard," mum said.
Преобразование:
Mum said that the kids had played tennis in the yard.
Или, опуская 'that':
Mum said the kids had played tennis in the yard.
Мама сказала, что дети играли в теннис во дворе.
Ответ: Mum said that the kids had played tennis in the yard.