not able to read iPhoto from external drive

i got a new macbook pro and decided to transfer all my photos from the older laptop to an external drive in order to manage them on my new one. i have not been able to open the iPhoto files on my new macbook pro. when i hook up the external drive, a window comes up saying i need to upgrade to a new version. i click on the upgrade button and another window comes up saying that it cannot open the iPhoto library because they are not supported on the new version, then forces me to quit.

i know the files are in the external drive because i can open them in the old computer.

any ideas on how to solve this problem?

How is this external drive formatted?

external drive

its a passport and its formatted for mac. i can open the iPhoto library from the external drive in the old computer which has an iPhoto 9. the new computer has the iPhoto 11. I'm afraid if i upgrade the old computer i won't be able to see them anywhere. i don't know what the solution is. i have over 28,000 pictures there!

thanks for reply.