How can I merge two user accounts and preserve the files of the old one? (docs, photo library)

Hello and thanks for your time.

I have recently upgraded from my trusty Macbook Air 2012 to the shiny new Macbook Air M2 2022. It took 10 years but finally the old one became glitchy, restarted intermittently, and the screen became a random pixelated mess. I could not use migration assistant to transfer all the data to my new computer because of these issues.

The Geniuses were able to use the thunderbolt connection to create a second user on my new computer with migration assistant successfully with the old information but I don't want it to be a separate user to access my old photo library and documents folder. I want to merge these two users and not lose any information.

How can I merge the two users on Mac OS with the goal of moving the documents folder and photo library to my new user, and then delete the old user?

Please advise me.

Thanks for taking the time.