How to identify what module should be loaded

Hi Im new to PowerShell, 

How can I identify what module to load from a specific command,

In MSDN Library for C# they have a portion in the webpage what assembly should be loaded if you want to use a specific class. I would like to know the appropriate module to load as im not yet familiar with the libraries of powershell.

For instance, im looking at this page "http://technet.microsoft.com/en-us/library/jj590708.aspx", and im having problem executing the command.

PS C:\Users\sheen.lim> Get-DhcpServerv4Reservation -computername mytestserver.limdynasty.com -scopeid 10.52.115.0
The term 'Get-DhcpServerv4Reservation' is not recognized as the name of a cmdlet, functi
on, script file, or operable program. Check the spelling of the name, or if a path was i
ncluded, verify that the path is correct and try again.
At line:1 char:28
+ Get-DhcpServerv4Reservation <<<<  -computername phcdoad02.ph.gbsorg.net -scopeid 10.52
.115.0
    + CategoryInfo          : ObjectNotFound: (Get-DhcpServerv4Reservation:String) [],  
   CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException