You can do a full system import only. If you intend to use a project import (as suggested by "merge" in your question), then you will need to upgrade your 5.1 data to 6.4 before exporting it, such as by setting up a new 6.4 instance and importing it there, then exporting it from there to use for the project import.
Hey Community mates! Claire here from the Software Product Marketing team. We all know software development changes rapidly, and it's often tough to keep up. But from our research, we've found the h...
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