Please see this previous discussion thread on the same topic:
https://community.home-assistant.io/t/zha-to-zigbee2mqttt-migration-using-backup-file
Same question has also been asked and answered in the official Zigbee2MQTT discussion forum here:
If have only around 10 devices then do would not think I bother unless it was just for the challenge of it.
Read + follow → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage