Hi Kshitija,
Use the JIRA Backup Manager.
https://confluence.atlassian.com/adminjiracloud/exporting-issues-776636787.html#Exportingissues-JIRABackupManager
Also refer to the below documentation that will help you automate the task.
https://confluence.atlassian.com/jirakb/how-to-automate-backups-for-jira-cloud-applications-779160659.html
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