Broken down:
- Get-cluster "cluster01" - start by getting the cluster
 - get-vmhost - get all the ESXi hosts in the cluster
 - sort-object name - optional to sort the hosts by name
 - get-datastore - get the datastores attached to the hosts
 - where-object {$_.CapacityGB -lt 10} - filters only the small datastores*.
 - Select-object - pick the properties to display
 - @{n="host";e={($_ | get-vmhost | select name).name}} - shows the name of the vmhost
 - name - shows the name of the datastore object
 - @{n="NAA";e={($_ | get-scsilun | select canonicalname).canonicalname}} - shows the naa of the datastore
 
Not all the fields may display completely on your screen. You can always pipe to out-file to dump the info to a text file or pipe to format-list
Sample output:
host Name NAA
---- ---- ---
hostab01 hostab01-boot naa.6005076801818...
hostab02 hostab02-boot naa.6005076801818...
hostab03 hostab03-boot naa.6005076801808...
hostab04 hostab04-boot naa.6005076801808...
hostab05 hostab05-boot naa.6005076801808...