Convert FXP to MP3

Converting FX Preset Files directly to MP3 Audio Files (.fxp to .mp3 conversion) is not possible, because these FXP files do not contain actual audio data, but rather consist of individual audio effects. Those can be added to several modern Digital Audio Workstation (DAW) projects.

You can add FXP presets to projects in tools, such as Cubase or Ableton Live, then bounce and export them in MP3 format. 

Simply put, it is impossible to convert FXP to MP3 directly.
Thus, there is no so-called fxp to mp3 converter or a free online .fxp to .mp3 converter to be found.