Age of Empires IV: Anniversary Edition

The Malians have a unique building in age II (feudal age) called a Cattle Ranch. You will need to build 7 of these to get this achievement and they cost 100 wood each. Once you build the 7 cattle ranches, next build a Mill. The Mill is where you create cattle to then put then in the ranch. Once you have the Mill create 20 cattle from there and put 3 in each of the cattle ranches you built. The maximum is 3 in each which is why you needed 7.

Like all achievements in this game you may need to wait a few minutes but it will pop at some point when you have 20 cattle in their respective ranches at the same time. Also like everything else, this works on a Skirmish map vs AI with resources set to maximum to make things easier.