Select naming series based on group

Hi,
I want to write custom script that will fill Series field(while creating new item) based on field in selected item group.
For now I did next:
Created all naming series I want to use.
Created field in item group doctype as select list.

Now I’m stuck with custom script.

frappe.ui.form.on('Item', {
refresh(frm) {
	
},

item_group(frm) {
   cur_frm.add_fetch('item_group','naming_series','naming_series') 
}

})