You can download the song "What If (I Told You I Like You)" by Johnny Orlando featuring Mackenzie Ziegler in MP3 format from several online platforms. Some options include:

• Highlifeng.com offers free downloads of the song in audio MP3 format.
• Boomplay provides streaming and free downloads for the song and album.
• Mdundo.com also allows downloading and streaming with high-quality MP3.
• There are also versions like remixes available on Mdundo and other streaming services.
• You can also find the official music video with lyrics on YouTube.

These platforms provide legal access for streaming or downloading the track in MP3 format.