Accessing Photos from iPhoto on Old Hard Drive

Have you tried to open your iPhoto Libraries in Photos? Which system version do you have installed on your Mac?

It will depend on the version of iPhoto that you have been using to work with the library and on your system version, how the Photos.app can access the photos in your iPhoto Library. See: How to access Media in iPhoto Libraries … - Apple Community

Fotos for Mac can work with iPhoto Libraries from iPhoto '09 (version 8.x.x.) and iPhoto '11 (version 9.x.x). Older iPhoto Libraries need to be prepared with the iPhoto Library upgrader tool. iPhoto '11: About the Library Upgrader . This tool contains 32bit code can only run macOS 10.14 or earlier. If your iPhoto Library is from an older iPhoto version you will need to prepare the old libraries on a mac with an older system version.

• On OS X 10.10.3 Yosemite to macOS 12 Monterey you can open iPhoto '09 and iPhoto '11 Libraries in Fotos and convert them to Photos Libraries for easy access to your photos. This will preserve the structure of the library as albums and folders.
• On macOS 13 you can no longer migrate iPhoto Libraries to Photos in Photos, but you can import the photos and videos into Photos Libraries. But you will lose the structure of the library.

Make sure you are clicking on an iPhoto library icon and not the iPhoto application icon. Let us know what top-level contents you are seeing inside the package. Maybe somebody here will recognize what old version of the library format you have.