Bug/Issue Stacks?

In my inventory and in chests, my items no longer show up as stacks? I can take an item from a stack individually, but there is no little number in the corner to tell me how many items I have in a stack?

 

It sounds like you installed an outdated XNB mod. (XNB mods are the ones which replace your game files directly, and are no longer recommended.) You can reset your content files to fix that, and I suggest avoiding XNB mods since they can cause issues like that. You can find Content Patcher versions for many older XNB mods here.