Where can I get myatmo v1?

Solution

According to Apple's AppStore policy, all AppStore users are encouraged to back up their devices through iTunes software or the iCloud to back up purchased apps.

If such a backup exists, and if such a backup contains myatmo v1, then myatmo v1 can be recovered from this backup and then used again. myatmo v1 is no longer available through the AppStore because Apple does not offer a download of old app versions.