Creating a bigger grid in Adobe Express

Hello ! I am using Adobe Express to make grids of 3 squared images per row with the grid tool, but I wish to make a longer grid with at least 9 rows (with 3 images per row), but none of the grid templates offer it. I've tried making my own template by grouping squared images together but each row automatically contain more than 3 images, and they turned out rectangle, wich is not what I'm trying to do. I am a bit hopeless here... 

I hope I was clear, and thank you so much for helping me ! 

- Lia