I would strongly suggest not to implement such logic for retrieving lost password.
You should at no point display password in clear text (avoid storing clear passwords in DB too!)
For lost password case, either you send an email with new random password generated for the account or send old password to registered email.
Displaying password on screen is a big security loop hole.
Yet, if you want to, based on what you have shared, it looks like you try to get a password for given email address.
1. Get email address from user
2. Get password for the email from database
3. Show the data returned in step 2.
For 2 & 3, use ADO.NET, following article will help:
Beginners guide to accessing SQL Server through C#
Accessing data with ADO.NET