Hi
You cannot replicate or backup/restore between dissimmilar versions of ACS.
The only way to migrate information is to
1.Take backup of old server
2. install same old version of ACS on new server.
3. restore Backup on this server
4. upgrade this server to ACS v4.1,
ACS 4.1 is only upgradable from ACS v3.3 or v4.0, any other version has to be upgraded to v3.3 before upgrading to v4.1
You can check following link for upgrade requirements:
http://www.cisco.com/univercd/cc/td/doc/product/access/acs_soft/csacs4nt/acs41/igwin41/install.htm#wp1052888
5. Backup the database
6. Restore it on new server
Hope this Helps
~Rohit