Older messages didn’t transfer to new phone (12 pro max)

Hi, when I transferred everything from my iPhone 11 to my 12 pro max it didn't transfer all of my messages. I didn't realize until I'd been using the new one for a while that it hadn't transferred older messages, it only goes back a few months. I need access to those older messages and they’re still in my old phone but I need to wipe that phone so I can set it up for my kids. Is there a way to keep the messages on iCloud or somewhere so that I can access them as needed? I don’t need them on my new phone necessarily, I just need to be able to access them.