Hiya Triona!
Thank you for bringing your question to the Disney Parks Moms Panel. I feel like any time I visit
The Happiest Place on Earth I'm always wishing to upgrade either to a hopper or to include one more day, so I'm glad
ticket upgrades are so easy and simple!
You can upgrade your ticket at any point that you still have valid admissions remaining. You can either upgrade directly on the
Disneyland Mobile App or by visiting one of the main entrance ticket booths in the esplanade between
Disneyland Park and
Disney California Adventure Park. I do want to let you know though, when upgrading a multiple day ticket, you will pay the difference for the total days that were initially on the ticket not the remaining days. For example, if you have a
four day single park per day ticket and you'd like to upgrade to a park hopper ticket, no matter what point in your stay you upgrade you will pay the difference between a four day single park and four day hopper ticket. For this reason, it's best to upgrade immediately to get the most amount of days between the two, rather than later on.
I hope this helps to clarify your potential upgrade during your next visit! Please come back if we can help in any other way.
-Lindsey