Hello! I am not able to determine what is the problem while I'm trying to reconfigure system.
I only add code for touchpad tap from 63 to 78 lines in config.scm (see attachment).

# guix system reconfigure /etc/config.scm
/etc/config.scm:47:20: error: config: unbound variable
hint: Did you forget a `use-modules' form?

Please, what I need to use in use-modules section?
=========part f config.scm=========
(use-modules (gnu) (gnu system nss)
             (gnu system locale) ;;for locale-definition
             (gnu services desktop)
             ;;(gnu services dns) ;;for dnsmasq
             (srfi srfi-1) ;;for remove function
             (gnu services networking) ;;for remove ntp
             (gnu services avahi) ;;for remove avahi
             (gnu services xorg)
             ;;(gnu services databases);;for postgres
             (gnu packages admin) ;;for wpa_supplicant

)
(use-service-modules desktop)
(use-package-modules certs gnome)....

  (services (cons*  
                    ;;(service postgresql-service-type)
                    (xfce-desktop-service)
                    (modify-services      
                      ;;(remove (lambda (service)
                      ;;  (eq? (service-kind service)
                      ;;    wpa-supplicant-service-type))
                      ;;  (remove (lambda (service)
                      ;;    (eq? (service-kind service)
                      ;;      static-networking-service-type))
                          (remove (lambda (service)
                            (eq? (service-kind service)
                              ntp-service-type))
                            (remove (lambda (service)
                              (eq? (service-kind service)
                                avahi-service-type))
                              %desktop-services

                                (slim-service-type config =>
                                              (slim-configuration
                                               (inherit config)
                                               (startx
                                                (xorg-start-command
                                                 #:configuration-file
                                                 (xorg-configuration-file
                                                  #:extra-config
                                                  '(
"Section \"InputClass\"
        Identifier \"touchpad-all\"
        MatchIsTouchpad \"on\"
        Option \"Tapping\" \"on\"
EndSection"
                                 ))))))


                            )  ;end of remove avahi
                          )  ;end of remove2 ntp
                        ;;)  ;end of remove3 networking
                      ;)  ;end of remove4 wpa-supplicant
                      (elogind-service-type
                        c => (elogind-configuration (handle-lid-switch 'ignore)))
                    );;end of modify desktop-services
  ));;end of services====================