To manage the number of product rows
displayed in the Product Detail screen go to the Design tab and click
Themes in your admin panel. Next, select the theme that you need to
edit. Once you are in the Theme, look in the left section under General
Settings and find Product Listing.
Click on the title and the Product Listing settings will unfold with the
Number of Rows option displayed as shown below. Enter the number of
rows that you want displayed and lastly, click Save Themes Settings.