What is the best way to test three different versions of a piece of copy?

Being very new to this field, I thought experts here could show me how to test this.

We have three different copies of an appstore description and we would like to see which one leads to more downloading. They are similar to each other, not drastically different.

I thought of usability hub, but the cost limits the number of users we can test.

So, what is the best way to hold this testing with a high number of people?