Hi @Sherry Kinch welcome to the Jira Cloud community. Hope you are doing good and staying safe.
I'm able to pull this link for your query: https://support.atlassian.com/jira-software-cloud/docs/migrate-between-next-gen-and-classic-projects/
Request you to thoroughly read the article as the loss of data might be due to any filters applied or missed query. If you feel you still needed a support, don't hesitate to reach: https://support.atlassian.com/contact/#/
If my post addressed your query, kindly upvote and click "accept answer", so new members can benefit.
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