CMD:admins(playerid, params[])
{
    foreach(Player, i) // Make sure you have the 'foreach' include as well. if not, you can use for(new i = 0; i < MAX_PLAYERS; i++)
    {
        if(PlayerInfo[i][pAdmin] >= 1) // or 2, your choice
        {
            // Assuming you don't have a function to get the players name, like RPN, or GetPlayerNameEx
            new pname[MAX_PLAYER_NAME], string[256];
            GetPlayerName(i, pname, sizeof(pname));
            format(string, sizeof(string), "Admin %s", pname);
            SendClientMessage(playerid, -1, string);
        }
    }
    return 1;
}