Error when try connect to mssql server database

Could you pls help on to connect mssql server database? I'm getting following error when i just click on "Connect" with default URI. (" mssql://user:password@localhost/INSTANCE/database?encrypt=true ")

Knex:Error Failed to connect to localhost:undefined in 15000ms

stack: ConnectionError: Failed to connect to localhost:undefined in 15000ms

at Connection.<anonymous> (C:\Users\KelumDesktop\AppData\Local\Programs" +

"osqlbooster4mongo\resources\app.asar" +

"ode_modules\mssql\lib edious.js:378:25)

at Object.onceWrapper (events.js:273:13)

at Connection.emit (events.js:182:13)

at Connection.connectTimeout (C:\Users\KelumDesktop\AppData\Local\Programs" +

"osqlbooster4mongo\resources\app.asar" +

"ode_modules edious\lib\connection.js:467:12)

How should i change the URI?

Assume my details are as follows;

Windows user name- my_user

Windows Password - Mypassword123

SQL server name - DESKTOP-ABCDEFG\SQLEXPRESS

Database name - mydatabase

Appreciate if you can help me on this?