Application authentication issue when hosted on IIS

There is requirement of application migration on different server.On current server it is working fine.
I migrated and hosted it on iis, when i browse application it is asking for windows authentication.

Also,connection string in web config doesn't contain user credential details.And when I try to access that database it wont allow me to access.

Please help from where to get user details to access this website.

Thanks,
bharati