Yes, you need an image that includes 3DES in the feature set. For example, when you go to the download page and you see a "IP PLUS IPSEC 3DES" feature set, then you know that this image includes 3DES support. In case you have already downloaded the image and running on the router, you can do a "show version" and look for the file name:c3745-ik9s-mz.123-24.bin and see a K9 in the name, you know that it contains support for crypto support.
Can you post the show version output from the router in question, so we can assist you with the feature set.
Regards,
Arul