I am looking for a tool or software with which I can import BaaN-data into Hyperion.

Any suggestions?

I thought Hyperion supplied there own exchange schemes for exporting data from BaaN? That is, if you have Hyperion loaded on your BaaN system, the exchange schemes should have the file format(s) required.
At least ours did, but we wrote our own BaaN session, which greatly reduced the time of creating the export file. We generate a ASCII delimited file (Hyperion used a comma delimiter) from BaaN in the format expected by Hyperion (based on the exchange schemes).

Hyperion should already have a tool (command) to import a ASCII delimited file.

The Hyperion Tool is called Ledger Link and it comes standard with the Enterprise package.
Regards,
BB