How would I get the info of a particular type of objects in a particular trigger in Unity3d

I want to change a thing based on the number of players of each teams in a trigger.

I'm thinking of getting the info of all the objects in the trigger access their tags and identify how many players of each teams are present in that trigger. But I can't find anything to do this.

Init team counts as 0:

int team1 = 0;
int team2 = 0;

Increase/decrease team count on trigger callbacks. Here you can use tags or whatever you prefer. I recommend having the team information in a script:

void OnTriggerEnter(Collider other)
{
    Player player = other.gameObject.GetComponent<Player>();
    if(player == null) return;
    if(player.team == 1) team1++;
    else team2++;
}

void OnTriggerExit(Collider other)
{
    Player player = other.gameObject.GetComponent<Player>();
    if(player == null) return;
    if(player.team == 1) team1--;
    else team2--;
}

And lastly, do what you want with your team counts:

void Update()
{
    //use team1 and team2 the way you want
}