I'm not familiar with the motorized back but, put the darkslide in, pull the battery, then remove the back from the camera. If the darkslide will not go in pull the battery, take the camera into a totally dark room, open the back, pull the insert out, and roll the film up and secure with tape or a rubber band.
READ psot 13 of
https://www.photrio.com/forum/threads/curious-advance-120-roll-2-rounds.167612/
In p;ace of a 620 spool use a empty 120 spool.
Correct the lens mounting as needed, dry fire the body/lens combo to verify it is working in sync then reinstall the back then the battery.
If the battery cannot be removed from the back then turn its power switch OFF and leave it off until ready to load a roll of film.