<template>
       <lightning-card>
        <lightning-combobox>
            label="Folders"
            value={value}            
            options={folders}
            onchange={handleChange}
        </lightning-combobox>
        
        </lightning-card>
       
</template>

Js.File

import { LightningElement,wire,track } from 'lwc';
import getFolder from '@salesforce/apex/EmailTemplates.getFolder'
export default class AddTempalte extends LightningElement {
    
    value = '';
    @track folders = [];
    

   
    @wire (getFolder) wiredgetfolder({data, error}){
        //console.log('Get the Folder deatails@@@'+JSON.stringify(data))
        if(data){
            console.log('Get the Folder deatails@@@'+JSON.stringify(data))
            this.folders = data.map(a=>({
                 label : a.Name,
                 value : a.Name
            }));
            console.log('Get the folder values &&&'+this.folders);
        }
        else if(error){
            console.log('Get the error details are @@@'+error)
        }
    }
   
    handleChange(event){
        console.log('Get the folder values'+this.folders);
        this.value  = event.detail.value;
    }
        
}