var oldUsers = [{
    "SID": "S-12",
        "Username": "bring.on",
        "firstname": "bring",
        "lastname": "on",
        "email": "emasdklhsjas@gmnailasd.com"
    // and so on... 10 more properties
}, {
    "SID": "S-13",
        "Username": "bring.on1",
        "firstname": "bring",
        "lastname": "on1",
        "email": "sdf@gmnailasd.com"
    // and so on... 10 more properties
},
              // n numbers of more users...];

var newUsers = [{ FullName : "bring on - emasdklhsjas@gmnailasd.com",
                 value : S-12
               },
              { FullName : "bring on1 - sdf@gmnailasd.com",
                 value : S-13
               }, // more users with same properties as abvove
              ];

var newUsers = $.each(oldUser, function () {
    return u = {
        value : this.SID,
        FullName : this.firstname + " " + this.lastname + " - " + this.email,
    };
});