Combobox selects State and city search in MySQL

I need to solve this part, my intention is to select the state in the combobox the query below recognize the selected acronym and query in MySQL.

function BuscaDAO(connection){
    this._connection = connection;
}

BuscaDAO.prototype.getBusca = function(state_uf, callback){
    console.log(state_uf.state_uf);
    this._connection.query('select state_uf from cities where state_uf = ' + 
    state_uf.state_uf1, callback);
}