Did you keep your photos in a Photos Library on your old Mac Mini? Or did you use iPhoto or Aperture, or another software to manage the photos on the old Mac?
If the photos are in any kind of Photo Library in the old user account, you should find a package called Photos Library.photoslibrary, or iPhoto Library.photolibrary, or Aperture Library.aplibrary in your Pictures folder.
The icon will be a fan of three pictures. Move this library to the folder /Users/Shared, not the complete Pictures folder.
Then sign into your new user account and move the "Photos Library.photoslibrary" from the folder /Users/Shared to the Pictures folder in your new home folder. If you already have a Photos Library there, rename it, so you do not overwrite it.
It would have been much easier, if you migrated your user account using Setup Assistent, immediately after you started up the new Mac the first time, before you created a new user account on the new Mac. The Photos Library from the old account, and all its internal files, will have the file ownership of the old user account, and the new user will not be able to open it directly. Before you can use it with Photos from the new account, the permissions and file ownership need to be repaired, not only for the library, but for all internal files as well. You can do that by repairing the library. See this Help page on how to repair a Photos Library: https://support.apple.com/en-gb/guide/photos/repair-the-library-pht6be18f93/mac
You can switch between two separate libraries by double-clicking the library you want to open.
Photos has no tools to import one library into another library, bt there are work-arounds, see:
Notes on Merging Photos Libraries