Currently, there's no feature to change a campaign type once you've created it (for example, a regular campaign to auto-resend).
However, you can reuse campaigns, so you won't need to start from scratch.
How to reuse an email
How to reuse an email
Create a new campaign
On the Email design step, go to the Recent emails tab
Click Sent/Drafts/Automations to find the email
Hover on the email you want and click the Select button
How to reuse a draft campaign and use it in an automation
How to reuse a draft campaign and use it in an automation
Create an email in your automation by clicking the + icon
(make sure the automation is turned off/paused to see the + icon)Enter a subject and other details, then click Design email
Click Recent emails
Click Sent/Drafts/Automations to find the email
Hover on the email you want and click the Select button
💡 You can also save a campaign as a Template so you can reuse it! Here, find a complete guide: Everything About Email Templates