YOU SAID:

I've completely forgotten what I was supposed to type here

INTO JAPANESE

私はここに入力するはずだったものを全く忘れた

BACK INTO ENGLISH

I completely forgot what I was supposed to enter here

INTO JAPANESE

私がここに入るはずのものを完全に忘れてしまった

BACK INTO ENGLISH

I completely forgot what I should enter here

INTO JAPANESE

私はここに入るべきものを完全に忘れてしまった

BACK INTO ENGLISH

I completely forgot what to enter here

INTO JAPANESE

私はここに何を入れるべきかを完全に忘れていた

BACK INTO ENGLISH

I completely forgot what to put here

INTO JAPANESE

私はここに何を入れるべきかを完全に忘れていた

BACK INTO ENGLISH

I completely forgot what to put here