Visual Studio can connect to any # of Azure DevOps, GitHub, Azure DevOps Server instances.
For an Azure DevOps Server instance go to Team \ Manage Connections
. Click the Manage Connection
link and it'll pop up the Connect to a Project
UI.
Click the Add Azure DevOps Server
link and type in the URL to your local instance. It will show up in the tree view along with all the other source control instances you are connected to.
The larger question is getting your VSS stuff into Azure DevOps. In general you should prefer to use Git over the older Team Project solution. This will make it consistent with other providers. There isn't necessarily an easy way to do this. Since Git is repository based I would recommend that each of your "deployable" projects in VSS become repos. However you may need to adjust it later. What I would strongly recommend is that you bring across your existing code with as little change as possible and get it checked in as your initial version. Then you can proceed to make adjustments to fit into the Git world. If your VSS stuff isn't too large you could even create a "legacy" repo and just drop everything into there. Then create new repos for work going forward.