Counting Files in Remote location using sftp in shell script

Getting Error with the below command to check on the Remote directory a specific type of files. The requirement is to get the count of the specific files. file_exists=$(sftp $FTP_UNAME@$FTP_HOST ls *$FILE_ID*.txt | wc -l) Is this not properly written? Please help... Below is the Usage Tip - usage: sftp [-1246aCfpqrv] [-B buffer_size] [-b batchfile] [-c cipher] [-D sftp_server_path] [-F ssh_config] [-i identity_file] [-l limit] [-o ssh_option] [-P port] [-R num_requests] [-S program] [-s subsystem | sftp_server] host sftp [user@]host[:file ...] sftp [user@]host[:dir[/]] sftp -b batchfile [user@]host