How to make content display in three columns instead of one column?

I am a beginner and learning from a tutorial using an API. I would like to change the layout of the design, and instead of having one column, I would like a three column layout. I don’t know if I am using flexbox correctly.

I have tried using row and then having three columns, but somehow its not displaying correctly.I am also using bootstrap.

jsfiddle.net/e5bqsywk/2/