Hello, Mahsa! Thanks for stopping by planDisney!
Many tickets that were purchased before the Disneyland Resort closed due to the pandemic have had their expiration dates automatically extended. For example, if you used one day of your three-day ticket between February 28, 2020 and March 13, 2020, you will have until December 16, 2021 to use the remaining days on your ticket. If you visited prior to February 28, 2020, then unfortunately your ticket would have expired 13 days after that first use.
If you visited within the time frame above, plan to visit the Disneyland Resort soon! The first thing you will need to do is link your ticket to your Disneyland Resort account. You can do this on the Disneyland app or by clicking the "Link Tickets" link under the "My Disneyland" menu on the Disneyland Resort website. Then, you will need to
make theme park reservations for each day you want to visit. You can check the
theme park reservation availability calendar to see if there is availability before making any plans.
I hope this helps and that you have an amazing time at the Happiest Place on Earth!
-Linda