I don’t know if there is a script existing but it is fairly easy.
Inside your site copy the complete content from “~/var/pnp4nagios/perfdata” to the new empty instance.
You can do this at a running instance but will loose around 1-2 hours of performance data. If this is ok then you can move your hosts after the copy job is complete to the new site.
If you need all performance data then you need first to flush the rrdcached.
This can be done with
echo "FLUSHALL" | unixcat ~/tmprun/rrdcached.sock
Wait some time and then copy the content as before. Loose here is only some minutes of performance data.