Ever tried Multcloud?
https://www.multcloud.com
"You can get started with creating an account with MultCloud and activating it. Once you have signed in to your account, it will ask you to add your first cloud storage drive. Select Google Drive from the list and grant MultCloud permission over your Drive (there’s no way to do it without granting it permission, but it uses OAuth so relatively safe).
Once you have connected the account, you will see all the files and folders in MultCloud. You can manage files using the MultCloud dashboard, however in order to transfer the files, we will need to add another cloud account you wish to transfer the files from.
To add the second account, click on the option
Add Cloud Drives in the left sidebar and select the cloud service you are currently using. After you add the second account, just put a check against all the folders you would like to move to your Google Drive and select copy.
Having done that, navigate to Google Drive and paste the content to the desired folder. Now all you need to do is sit back and wait. MultCloud will copy all the files from one account to another without wasting your bandwidth and you can continue with your work. If you want to see the progress, you can pin the tab on your browser.
Using MultCloud you can manage multiple cloud storage accounts without any restriction other than the maximum file size processing which is 200 MB at the moment. Although this limitation is mentioned in their support page,
I was able to transfer video files as big as 1.21 GB using the service.
The service claims to neither store your login credentials nor the files you worked on. All the transfers are done with 256-bit encryption and the authorization system of MultCloud is based on OAuth."
https://www.quora.com/How-do-I-easily-transfer-all-my-files-from-Dropbox-to-Google-Drive
