Hi Arnoldo, welcome to planDisney!
Thanks for bringing your question to us, I am happy to help!
You can certainly update your reservation to be from
Disney California Adventure Park to
Disneyland Park, but this will depend if there is reservation availability at Disneyland Park. So first and foremost, check the
Theme Park Reservation Availability Calendar to see if there is availability at Disneyland Park on the date you plan to visit.
If there is availability, you will need to cancel your current reservation by logging in to your
Disneyland Resort account, selecting the "My Disneyland" link, and then clicking the "Ticket and Reservation Details" link. Select the reservation you wish to cancel and click "Cancel Reservation". Once canceled, you're free to book your new reservation!
If you have any more questions, you know where to find us!
See ya real soon!
Jin