Upload old pictures into icloud

See the. above comment, enable syncing of photos on you Mac. See these reads: (iCloud) https://support.apple.com/guide/icloud/what-is-icloud-mm74e822f6de/icloud and (Photos and iCloud) https://support.apple.com/en-us/HT204264 and (if you need more storage) https://support.apple.com/en-us/HT201318

What is the file format of the old image files? iCloud photos only supports the file formats commonly used by digital cameras. when in diubt, convrt the images to JPEg or Tiff files. then use the upload button in the Ohoyos app at www.icloud.com to upload the files.