I have checked your problem. However, Motion is a paid theme so I cannot test it specifically, so I will guide you on the refresh theme because they are quite similar.
First, open the code editor, then find the file main-collection-product-grid.liquid (the names may be different, but find the file related to displaying the collection).
Then you find the line of code with the following content:
Thank you! Took a while but finally found it. For the motion it seems it’s a little different. Here is the code part where I changed the amount of rows (If somebody else is looking for this)
I’m using a 3rd party theme and am having trouble editing the code to add more products per row on my shop. I didn’t set up this theme so I’m unsure of how to proceed without completely building a new site from a shopify theme.
You can completely use your theme without needing to replace a new theme. You just need to find the file related to displaying the collection and edit it.
If you have problems editing, please provide the theme you are using, I can help you with that.