iPhoto Library in time machine backup, but can't open on new macbook - help

Here is the scenario. I just got a new macbook. My old macbook was stolen in a backpack along with an external HD I was traveling with. My old computer was full so I decided to transfer my iPhotos library to my external HD to clear up space (photos including many years of memories ever since my first iphone). Again, the computer and the external got stolen together.

I was hopeful to remember that my old time machine backups would have this library saved, safe at home during the travels when things got stolen. So I just started my new computer and was surprisingly only allowed to select my most recent time machine backup Sept 12 2019 before the travels so that is what I did...

Now from Finder 'locations' on my time machine external I can see the iPhoto library saved from May 3 2018 on the backup. I try to open it but "Photos was unable to open the library “iPhoto Library”. (3127)"

I am aware these are on different OSX and maybe that is the problem? What do you think?

But if I can see this library exists isn't there some way that I can access it and save all of my photo files?