how to find the users in left the company or left the project in JIRA development,
How are you recording the act of leaving?
If you're not, then all you can really do is look at a user's last login, or for a project, run searches for the last time they updated an issue in it.
I suggest when you deactivate them you move them to a group called something like 'obsolete users'. But as Nic said, if you're playing catch up it will require manual effort.
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