public int[] enemiesHealth;
public Vector3[] enemiesPositions;
public Vector3[] enemiesForwardVectors;

public int FindClosest(Vector3 position)
{
    float minDistance = float.MaxValue;
    int minIdx = -1;
    for(int i=0;i<10000;++i)
    {
        var enemyPosition = enemiesPositions[i];
        var distance = Vector3.Distance(enemyPosition,position);
        if(distance < minDistance)
        {
            minIdx = i;
            minDistance = distance;
        }
    }
    return minIdx;
}