Amruthoji,
There are multiple ways to extract data from cubes, the most popular being Open Hub or APD. Once the data is available in a file it can be uploaded to the new InfoCube in the new BW system.
Another option is to create an RFC connection between the 2 BW systems. Create an export datasource in the source BW system. The source BW system would need to be created as source system in the new BW system and when the DataSources are replicated the export datasource will show up which can now be linked to the new Cube in the New BW system.
For POC the first option is more suitable and the second option is advisable when large volumes of data are involved
Hope this helps
-Sid