"I went to the store to get my photos developed but they had already closed."
"I went to the shop to develop my photos but it had already closed."
"I went to get my photos developed but the shop had already closed."
"developed" - to develop 「現像する」
"already" 「すでに」
"store" と "shop" どちら使っても大丈夫で、"camera store" や "camera shop" も使えます。
一つ目の文 "...but they had already closed." の "they" はお店の店員さんがお店を閉店した事を表し、二つ目の文の "it" はお店がもう閉店した事を表します。
"photos" の代わりに "film" 「カメラフィルム」も使えます。"I went to the store to get my film developed..."
オーストラリア 
