Try stopping all VMs on the first environment and copying all VM artifacts (.cfg files and .img files) from the old repository (if you are using NFS repository it is a little bit easyer. If not, the repository is mounted anyway on each OVS so you can access it that way) to the new. The new OVM should recognize copied artifacts.
If you transfer a VM directly onto the new storage repository, you need to refresh the repository to have OVMM recognize the new files.
This isn't the case, if you import the files using the regular procedure.
If you search this forum, there has been a post describing how to transfer VMs easily from OVM 2.2.x to OVM 3.x.