How to enlarge thumbnails images in administration panel?

Hello,

I have a small online store made with Woocommerce and Shopkeeper. I would like to enlarge thumbnails images in my administration panel because the pictures are too small to manage my products. I only find some tutorials to enlarge thumbnails for the public visiting my page, but not for the administrator in the back office. Is it possible ? Can somebody explain me how I can enlarge my thumbnails images?