First IDS patch are not full installs, they are just patches to add new device support in the existing version. Both RME 3.3 and 3.4 have their own separate IDS patches which cannot be mixed n matched, meaning can't apply a 3.3 IDU over 3.4 install.
Secondly, from your description above, it looks like you have already RME 3.3 installed and you're planning to upgrade to RME 3.4 and want to preserve the data at the same time?. If this assumption is correct, then when I look at the RME 3.4 Install Guide on CCO (since you did not mention the OS that you're on, I'm just using Solaris as an example here, but the same is true for Windows as well):
Section 'Upgrading from a Previous Version': http://www.cisco.com/univercd/cc/td/doc/product/rtrmgmt/cw2000/cw2000e/e_3_x/3_4/install/solaris/solinstl.htm
I do not see above as where it says that you can only upgrade to 3.4 from 3.3 with IDS patch?
Lastly, to find out what version you're on and what IDS patch (if any) are installed, login to CW2K/RME then goto Server Configuration->About the Server->Applications and Versions and you'll see the details.