iPhoto Library and photos - Opening a file

Hello folks,

I have an old MacBook running Mavericks (10.9.5) which has an iPhoto Library file with almost 30000 items. I copied this file to another MacBook, running High Sierra (10.13.6) and with Photos.

I tried to open the iPhotos Library file and it goes well till more or less 20% when it stops due an error, but doesn't say what error

I don’t want and I cannot lose what is inside iPhoto Library, but need to transfer to the MacBook running High Sierra . Would anybody has an advice, guidance?

Thanks Paulo