Out-place-upgrade from 7.2 to 8.2

we have a customer sequence id for our cases. we are not using pc_data_uniqueid for ids or prefix. when we use the OOTB Package Work wizard to migrate the instances of the case from 7.2 to 8.2.

the wizard expects the id range including the prefix without that we can not proceed so ours is the custom id. the prefix and id both dynamically generated. so it is not a constant to build that we gave 1 and 500 to see how those instances come, the product rule that comes out of the package wizard as the when rule using those id range parameters.

if I remove that when the rule in product file and clicking on the preview product file button shows the instances but if I keep and clicking on the preview product file button does not show the instances.

I removed the when rule and exported and imported to the target system nothing happens with no errors in the log. Any idea.

tried one case instance data copying from the one version to another through DB backend everything seems to be working but we are not sure that is the right approach to do it.

How to make this work. what are the best practices for data migration from one version of Pega to another version of Pega?

Thanks in advance.