We do have option to export your data in csv format and available under respective service tab in AppHQ console.
We are adding the support of import data option for stoarge and would be available by next week release.
Also, if you have urgent request to migrate your data, drop me an email on ajay.tiwari@shephertz.com. We will help you in migrating your data from other backend provider to App42 and if required we can write a needed script for the same for given data format.
Let me know if it helps.
Thanks
Ajay