Problem with checking animation is done already or not

im new to unity, and still understanding a few aspect of it.. i have HeroIdle and HeroAttack Animation. i've set transition after attack and back to idle..

i need to loop attack animation a few times, and back to idle after that. what ive tried :

 loop 20 times
     {
         if(first loop)
         {
             _animator.Play("HeroAttack");
         }
         else if(_animator.GetCurrentAnimatorStateInfo(0).IsName("HeroAttack")) //is always returning false
         {
             _animator.Play("HeroAttack");
         } 
     }

so i started to track the problem. and i've found other problem. i tried to delete the transition after HeroAttack back to idle.

 loop 20 times
 {
     if(before last loop)
     {
         _animator.Play("HeroAttack");
     }
     else if(last loop)
     {
         _animator.Play("HeroIdle"); //its always playing Attack animation
     }    
 
 }

how does unity animations work? and how to solve my first problem?

i really want to learn unity, because after participating in global game jam, unity programmer can produce game faster than mine. previously cocos2d-x but i still didnt know a few things about it. any help is appreciated. or perhaps anyone has any social media account, so i can ask more :3 thanks