you can directly use the secure string as it is in type secure text activity, or in assign activity which also expects a secure string…
however, you can use several logics to transform the data in the secure string to a normal string as well. That will allow you to use that data in other places. but I don’t think this is a good approach as secure string usually contains passwords.
So for your scenario, i think you will need to convert the secure string to a string to use in the connection string you have built there…
For that, refer to this