If you are migrating from version 22.214.171.124.0 to 126.96.36.199.1, nothing will be erased and all your targets remains intacted. Just do upgrade with newer version of plug-in without un-installing older version of plug-in.
If you are migrating from 188.8.131.52.0 to 184.108.40.206.1, all the targets have to be removed first, un-install the current plug-in and then upgrade.
Please refer NetApp plug-in IAG guide for more details for upgrade scenarios.
Can you please share what version of OEM12c is deployed in your environment and current version of NetApp Storage plug-in?