Connecton string when connecting to sql server

I am trying to connect to a sql database in an aspnet .identity web forms project. The original sql express used

<add name="DefaultConnection" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-bigdogpro-20170301013515.mdf;Initial Catalog=aspnet-bigdogpro-20170301013515;Integrated Security=True" providerName="System.Data.SqlClient" />

I tried this, the string used in the old version of the site.
    <add name ="DefaultConnection" connectionString="DESKTOP-8371SA1;Initial Catalog=bigdog;Integrated Security=True" providerName="System.Data.SqlClient" />

This returns this error: Keyword not supported: 'desktop-8371sa1;initial catalog'.

Is there more to the connection      in this case?