not getting the mailbox command on cmdLet

Hi all,

I am going to Uninstall the Exchange server 2013. It was fresh installation and i never configured all roles. But now i have uninstall and install on other system. so i am uninstalling and getting the below error while removing the mailbox.

xxxxxx:> Get-Mailbox -Database 1853738799 
Get-Mailbox : The term 'Get-Mailbox' is not recognized as the name of a cmdlet, function, script file, or operable
program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ Get-Mailbox -Database 1853738799 -PublicFolder
+ ~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (Get-Mailbox:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

PS C:xxxxxx> Get-Mailbox -Database 1853738799
Get-Mailbox : The term 'Get-Mailbox' is not recognized as the name of a cmdlet, function, script file, or operable
program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ Get-Mailbox -Database 1853738799
+ ~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (Get-Mailbox:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException