YOU SAID:

I can't remember what I had to eat for dinner on monday

INTO JAPANESE

月曜日の夕食に食べたものを覚えていません

BACK INTO ENGLISH

I do not remember what I ate for dinner on Monday

INTO JAPANESE

月曜日に夕食に食べたものを覚えていません

BACK INTO ENGLISH

I do not remember what I ate for dinner on Monday