Importing addresses into address book

I tried importing addresses from my G4 1.25 MDD, 10.3.9 - export/address book archive - to a G5 Dual 1.8, 10.5.6 but when I try to add the file to the G5 address book I get a message saying:

'Reverting will cause your current database to be overwritten.
The Address Book archive “Address Book M2 - 12/29/09.abbu” will be copied over your existing database. This operation can’t be undone.'

Is there a way to ADD to the newer address book and not overwrite it?

Thanks for any replies.