Best way to implement Item Set Bonuses?

I want to tie attributes to item sets, similar to autochess games. So if you have 2 items of the same type, you get a bonus, and then with 4 items of the same set you get a stronger bonus. However I am not sure where I should store the information for those bonuses. I thought I would have a set number of Attributes classes that each store a specific one, such as one that adds bonus damage called "Fire", and then assign any number of those attribute classes to each item. But would I need to make them static? Would those attribute classes be able to hold the info during combat that actually adds the damage?

Here is my base item class:

 public class Item: ScriptableObject
     {
       public string Name { get; set; }
       public GameObject Prefab { get; set; }
     
       public Sprite Icon { get; set; }
     
       public ItemStats Stats { get; set; }
       public Rarity Rarity { get; set; }
       public Attribute[] attributes { get; set; }
     }
 

Any help/advice is appreciated!