Hello, @Kazi Sabit,
Actually, the thing is that there is no option to set the thumbnail images for the mobile. The only option is for the desktop and by default for the mobile, it shows 4. In order to show all the images please make sure that you have enabled the slide for thumbnail option so that users can slide the thumbnail images to see more. Check the image: https://postimg.cc/LJs3YKfW. You can find this option in Theme Settings >> WooCommerce >> Single Product Builder >> Gallery.
Regards 8Themes Team.