Add this in your current theme functions.php

 remove_action( 'wpcfe_shipment_table_header', 'wpcmerch_admin_shipment_merchant_shipment_rate_header', 10);
 remove_action( 'wpcfe_shipment_table_data', 'wpcmerch_admin_shipment_merchant_shipment_rate_data', 10);
remove_action ( 'wpcmerch_before_delivery_cost', 'wpcmerch_delivery_total_cost', 10);
add_filter('wpcmerch_delivery_fields', 'custom_delivery_fields', 1);

function custom_delivery_fields($fields){
	
	  $fields     = array(
        'wpcmerch_store_name' => array(
            'label'			=> __("Store Name", 'wpcargo-merchant'),
            'field_type'	=> 'select',
            'required'		=> true,
            'options'		=>  wpcmerch_store_lists( get_current_user_id() ),
            'placeholder'   => __("Select Store", 'wpcargo-merchant'),
            'sub_info'      => '',
        )
    );
	return $fields;
}