This is a known scenario where we have added the necessary steps in the WSO2 IS upgrade documentation.
However the upgrade assistance is only provided to our paid customers. If you are a paid customer please reach us through our support, otherwise you will need to fill up a contact us form and get in contact with a sales representative of WSO2.

For further info, refer: https://is.docs.wso2.com/en/latest/deploy/upgrade/upgrade-wso2-is/