File C:\Users\umesh\AppData\Roaming\npm\yarn.ps1 code example
Example 1: AppData\Roaming\npm\react-native.ps1 cannot be loaded because running scripts is disabled on this system. For more information, see about_Execution_Policies at https:/go.microsoft.com/fwlink/?LinkID=135170.
Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy Unrestricted
Example 2: The file \AppData\Roaming\npm\yarn.ps1 is not digitally signed.
Remove yarn.ps1 from the directory C:\Users\%username%\AppData\Roaming\npm\ then try clearing the npm cache at C:\Users\%username%\AppData\Roaming\npm-cache\