Hi,
this is your data flow.
Data source--->cube1--->Cube2.
Using info pack you can load data to PSA and then Cube1.
if you loaded upto psa only then go to you PSA-->right click--> there you may see options like update to further targets. click on it, that will udpate to cube1.
your facing problem at cube1-->cube 2.
As per the 3.x first you need to convert you cube as data mart.
Go to your cube1-->right click-->generate export data source.
Now create update rules between cube 1 to cube2.
Later go to RSA1-->source system, find your bw system and expand it.
below bw source system you may find your data source name as 8cube1.
select 8cube1-->create info pack--> choose target as cube2 and execute it. it will load data to cube2.
Thanks