As you already have mongodb backup on Linux VM, you can use the AzCopy utility to move the mongodb backup to azure storage account.
Please refer this guide which has all the details on how to install, Authorize AzCopy methods and commands to move files to storage account.
To get this running automatically everyday, you can setup a cronjob to do this.
Also, I assume that you have a script for purging aged backup files to avoid piling of backup files on you vm overtime.
If this is not setup, you should include this as part of your daily back maintenance cycle in the automation you are setting up through a Linux script.
Hope this helps.
Please 'Accept as answer' if the provided information is helpful, so that it can help others in the community looking for help on similar topics.