Impossibile to store DiskNumber knowing the disk label

[Fasyrio]

PS C:\Users\utente> Get-Disk | Where-Object { $_.FriendlyName -eq 'XXXXX' }
PS C:\Users\utente>

Impossible is assign letter (Example b) a disk with label "XXXXX'

$DiskNumber = Get-Disk | Where-Object { $_.FriendlyName -eq 'XXXXX' }
Get-Partition -DiskNumber $($DiskNumber.Number) | Set-Partition - newDriveLetter b

[#2]

I follow the same cmdlets you used and was able to set a drive letter
what is the error you are getting..