You cannot do this with a simple scripting.
Use WinSCP .NET assembly from a PowerShell script.
https://winscp.net/eng/docs/library_powershell

Use Session.EnumerateRemoteFiles to find the list of matching files.
https://winscp.net/eng/docs/library_session_enumerateremotefiles

Dear Experts,

I am using the below code to download the file present on SFTP server path. I have to add a condition that if only 1 file is present than only it will download & in case more than 1 file is present then it should throw an error message. Any pointer on it?

::1 Download file from SFTP server to Local machine
ECHO Started downloading the files from ERP Cloud SFTP Server %date% %time% >> %logfile%
%WINSCP_EXE_PATH% /command ^
"option batch continue " ^
"option confirm off " ^
"open sftp://%INBOUND_SFTP_CONN%/ "^
"get %INBOUND_SFTP_PATH%*.txt " ^
"close " ^
"exit"

Regards,
Anchit