Format of the initialization string does not conform to specification starting at index 120.

You need to check your connection string in Web.Config File, basically it is throwing an error because of connection string format is not correct.

SQL Server Connection string formats

Standard Security

Server=myServerAddress;Database=myDataBase;User Id=myUsername;Password=myPassword;

Trusted Connection

Server=myServerAddress;Database=myDataBase;Trusted_Connection=True;

Connection to a SQL Server instance

The server/instance name syntax used in the server option is the same for all SQL Server connection strings.

Server=myServerName\myInstanceName;Database=myDataBase;User Id=myUsername;
Password=myPassword;

It should resolve your issue.

Or Check if You are updating the database using Code-first(Update-Database command ) if you have selected the correct project(Entity framework project) in NuGet package manager console or not, if not Nuget may be looking in at the web.config file of that startup or any other project.