Hey there, hi there, Arieyanna! Welcome to planDisney and thanks so much for bringing us your ticket question.
Oh boy! I'm sorry to hear that the date you are wanting to visit only has
theme park ticket reservations available for Disney California Adventure Park when you were wanting to visit Disneyland Resort instead. Unfortunately, this means that you cannot purchase a ticket for Disneyland Park for that date right now. This doesn't mean all hope is lost though! The calendar and reservation availability does change, so I highly suggest that you keep your eyes on it frequently because Disneyland Park reservations could show back up again. If you see it, do not waste any time and try to immediately secure it because chances are it won't last long if others are wanting Disneyland Park too.
Your other option would be to
purchase a Park Hopper ticket instead. At the time of writing this, both parks are available for Park Hopper tickets. I love having the ability to park hop since both parks are so close to each other. It really takes no time at all to walk out of one park and into the next. I've been known to park hop just for a specific snack!
Arieyanna, I am sorry you can't get the reservation you were wanting right now, but I am sending you pixie dust that some will open up for you!
Carrie