@esha1701 may not be the only way but I extract via the api, something like
curl -X GET "https://<nightscout-site>/api/v1/entries/sgv?count=20" >output-file
will pull the last 20 readings to a file called output-file.
more details on the api are on your nightscout site at https://<nightscout-site>/api-docs/
please note: most NS discussion has moved to discord at https://discord.gg/zg7CvCQ so you may be better posting there