The security advisory and FAQs show a way to get a hash value for the SolarWinds.Orion.Core.BusinessLayer.dll file that was hacked,
Get-FileHash "C:\Program Files (x86)\SolarWinds\Orion\SolarWinds.Orion.Core.BusinessLayer.dll"
However, this file is in more than one location, depending on what is installed on your system (I found it in 6 locations) . An easy way to find and check these is to modify their PowerShell command, I used:
Get-ChildItem -path c:\ -include solarwinds.orion.core.businesslayer.dll -recurse -ErrorAction SilentlyContinue
and
Get-ChildItem -path c:\ -include solarwinds.orion.core.businesslayer.dll -recurse -ErrorAction SilentlyContinue | Get-FileHash
the first command is needed, because the second one (that generates the hash) truncates the displayed path.