Hi Guidoc,
Are you able to pul the worn pads out and check the part number on the back? It should be printed on the smooth rear-facing metal surface.
Here is a helpful video that explains how to swap the pads. https://www.parktool.com/blog/repair-help/disc-brake-pad-removal-installation
Shimano makes XT calipers with two and four piston configurations for more or less braking power, and they use different size pads.
Hope that helps.