as

このカメラはあのカメラほど古くはありません。 This camera ＿＿ ＿＿ ★ ＿＿ old as that one.

The correct order is 'This camera is not as old as that one.'. The 3rd word (★) is 'as'.

正しい語順は This camera is not as old as that one. (not as + 形容詞 + as「〜ほど〜ではない（同等比較否定）」) となります。3番目の空白（★）には as が入ります。