Hello,
First of all thanks for choosing our Theme, we are glad to be you in the WoodMart WordPress family :)
Sorry but there is no option in Theme Settings to display 4 columns on mobile for products.
This is not a standard way because the mobile screens are less in width and the content will be distorted that’s why we have only two columns option for mobile screens. You can try adding the following Custom CSS in the Custom CSS for Mobile area under Theme Settings >> Custom CSS. And if it works fine for you then you can keep it otherwise it requires customizations.
.product-grid-item {
max-width: 25%;
}
Regards.
Xtemos Studios.