SharePoint Online loop and create subfolders

Dear all,

I am using a SharePoint Online document library to store documents stored per client.

I have a document set for each client. In total I have more than 500 document sets, all containing the same folder structure.

The document library is built up as follows:

1. Client A
   1. Invoices
   2. Correspondence
   3. Technical
   4. etc.
2. Client B
3. Client C
4. Client D
5. etc.

I would like to create another folder at the second level (where Invoices, Correspondence, etc. reside), named "Projects", and inside that new folder just a few subfolders.

I would like to do this automated, otherwise it would take me a lot of time. 

I have seen a few articles on the web, but I haven't found the exact same scenario yet. I know somehow this could be done using PowerShell and a loop? PnP? But I don't have enough knowledge and experience to adjust the solutions from the articles I found so it would fit my scenario.

What would be the best approach to accomplish this?

I hope that someone could help me out with this.

Thanks in advance for helping out!

Kind regards,

Joost