How do i spawn entities from prefab in runtime with ECS?

So i watched articles with this question, and everyone uses 'IGameConvertObjectToEntity' with default Unity 'ConvertToEntity' script.

As i understand we have to add GameObject and set prefab before, then it runs before scene loads and we have our Entity prefab ready. But what if i have, for example folder with 100 trees prefabs, with the names tree_1, tree_2, ... , tree_100, and i want to spawn new tree whenever user clicks mouse button, and randomize last number to get tree, in some system. How do i convert it properly to get entity with material and ect. that prefab used to have.

Is the code below possible?

 //pseudocode
 
 public void OnUpdate()
 {
     if(clicked)
     {
         prefab = GetTreeFromFolder("tree_" + rand(from 1 to 100))
         entity = convert(prefab)
         
         ...Instantiating and working with entity...
     }
 
 }
 //pseudocode