How to fetch files of JSON, apex and lwc in main salesforce org?

Hi @Hitesh Sharma, 

You can use 

After authorizing the org, use SFDX: Retrieve Source from Org in VS Code to retrieve the required components. 

For JSON files, it depends on where they are stored: 

• Static Resource/LWC bundle → retrieve the corresponding metadata. 
• Salesforce record/data → use SOQL, Data Loader, or another data-export tool. 

Hope this helps!