YOU SAID:

I was at a party yesterday.

INTO JAPANESE

私は昨日パーティーにいました。

BACK INTO ENGLISH

I was at the party yesterday.

INTO JAPANESE

私はパーティーに出席した。

BACK INTO ENGLISH

I was at the party.

INTO JAPANESE

私はパーティーに出席した。

BACK INTO ENGLISH

I was at the party.