It is not possible to convert subtitles (.srt) to audio (.mp3), which srt to mp3 conversion likely (supposedly) represents. However, you should be able to load these subtitles during media playback, for example in VLC player. It is worth mentioning that if you would export to .mp4 file instead, you would actually be able to embed subtitles to it.
Open SRT file Open MP3 fileAn online service for translation and transcription of text files