YOU SAID:

My dad said that he was going to get milk and never came back

INTO JAPANESE

私の父は彼がミルクを手に入れるつもりで、二度と戻ってこないと言った

BACK INTO ENGLISH

My dad said he was going to get the milk and would never come back

INTO JAPANESE

私の父は彼がミルクを手に入れるつもりで、二度と戻ってこないだろうと言いました

BACK INTO ENGLISH

My dad said he was going to get the milk and would never come back