As long as you’re logged into your Pro account, you can sync your downloads back or sync them to a new device anytime. Just go to the JioSaavn app settings > Pro Options > click on Sync Downloads.
Note: If some songs are missing, try searching for them within the JioSaavn app. If they're still not found, they might be temporarily unavailable. To learn more about music availability on JioSaavn, visit our music rights page at https://www.jiosaavn.com/corporate/music-rights.