You can convert a decimal WWN into a hexadecimal WWN with the .NET convert class. E.g. if the decimal WWN is 5764963215165882199 you can convert this with:
[convert]::ToString(5764963215165882199,16)
For the method to convert the result into a vendor/serial take a look at:
How to... interpret worldwide names
Regards, Robert
Blog: https://rvdnieuwendijk.com/ | Twitter: @rvdnieuwendijk | Author of: https://www.packtpub.com/virtualization-and-cloud/learning-powercli-second-edition