How to use old account

I have old account for jira and gerrit.
At some point, the unified account is required for them.
How can I use the old account for that? or Is there any step to convert the old one to unified one?
Temporarily, I created new unified account but it also fails to register e-mail for gerrit, because the old account still have the e-mail.
What I really want is to use my old account as a unified one.
Is it possible?