var table_row = $('table').find('tr#'+pid);
var name = table_row.find('td:nth-child(1)').html();
table_row.find('td:nth-child(6)').html('<button  type="button" id="what to write here" class ="save_db")>save</button> ');

var table_row = $('table').find('tr#'+pid);
var name = table_row.find('td:nth-child(1)').html();
table_row.find('td:nth-child(6)')
  .html('<button  type="button" id="'+name+'" class ="save_db">save</button> ');

table_row.find('td:nth-child(6)').html`(
    '<button  type="button" id="' + name + '" class ="save_db">save</button> '
)`;

table_row.find('td:nth-child(6)').html('<button  type="button" id="'+ name + '"
class ="save_db")>save</button>');

table_row.setAttribute("id", "id_you_like");

var id = "btn1";
var table_row = $('table').find('tr#'+pid);
var name = table_row.find('td:nth-child(1)').html();
table_row.find('td:nth-child(6)').html('<button  type="button" id="'+id+'" class ="save_db")>save</button> ');

<button type="button" id='"+name+"' class= "save_db">