Import 5K+ term set in SharePoint Online using CSOM

Hi there,

I'm looking for an inexperienced guide/walkthrough to import term store terms using CSOM or PowerShell. I have put together a term set for our purchasing and procurement team to use when purchasing products or services - see attachment for reference.  I couldn't import the term set using the CSV format in admin center. 

It seems that we can't import more than 5,000 items - https://docs.microsoft.com/en-us/sharepoint/troubleshoot/search/troubleshoot-error-when-importing-a-term-set

I've never used CSOM or PowerShell but I did download and install SharePoint client components sdk. There is an article which provides some information on how to do that, but I couldn't figure it out - https://blog.josephvelliah.com/o365-sharepoint-online-import-term-store-terms-using-csom-powershell

Hope someone can help out.

Thanks