Old iphoto library is not accessible 58,000 pictures I cannot view

This guide may help: https://discussions.apple.com/docs/DOC-8461

You likely need to repair your library in iPhoto on the old device and pay special attention to the use of photos library on external drives. Especially pay attention to the required file format: https://support.apple.com/en-us/HT201517

I would try repairing on the old machine and copying the library in it's entirety to the new Mac. Or, enable iCloud photos on both devices so that all of your pictures migrate; that process may take a few days and requires you to purchase iCloud storage space for at least one month.

You likely have your photos backed up to another drive using Time Machine. If not, you really should as you only have one copy of the data.

And, if nothing else works, all of your original pictures are still accessible within the actual library package (right-click and show package contents).

What format is the external drive? It needs to be formatted Mac OS Extended (Journaled) or apfs.

You are using Photos on the new Mac, right? iPhoto will not work on any OS past Mojave.