昔の友達に

to an old friend

→ 昔
phrase Rare #20,562
to an old friend 昔の友達 means “an old friend,” and に marks the person encountered, contacted, or otherwise directed toward. In these examples, it commonly appears with 会う or 出会う, meaning “run into an old friend.”
JA: 駅で昔の友達に偶然会った。
EN: I happened to run into an old friend at the station.

東京駅たまたま昔の友達に出会った

I happened to run into an old friend at Tokyo Station.

最終的に彼女は何とか昔の友達に連絡を取った

In the end, she somehow managed to get in touch with an old friend.

彼は昔の友達に会いに行ったにちがいない

He must have gone to see an old friend.

私は道で偶然昔の友達に出会った

I ran into an old friend by chance on the street.