Unable to run powershell command at SharePoint 2010 server

Issue:
Some time you might be getting the following error message while running the powershell command at SharePoint 2010 server.
The term "" is not recognized as the name of cmdlet, function, script file, or operable program....
Resolution:
Run the following command:
add-pssnapin Mricosoft.SharePoint.Powershell  and then Press enter

Command to migrate Huge Library

Issue:
While migrating a huge library it might be failing for number of times. The export will fail due to huge number of files, hence unable to import it at destination site
Resolution:
Use the command in exact format as:
stsadm.exe -o export -cabsize 1024 -includeusersecurity -versions 4 -url 'https://mysite.url/oldcollection/myweb' -filename myweb.cmp

cabsize can be from 10 to 1024