Download - The Say 123548 (1) Mp3

MP3 is an acronym and should be capitalized [2, 3].

Placing "MP3" before or after the title makes it clear that the file format is an MP3 [1, 2]. Download the say 123548 (1) mp3

Alternatively, if this is for a button or a direct instruction, you could use: "Download 'Say 123548 (1)' (MP3)" MP3 is an acronym and should be capitalized [2, 3]