Hi,
To convert an unsealed management pack .xml file to a .sln file for editing in Visual Studio, you will need to use the Service Manager Authoring Tool. The Authoring Tool allows you to create and modify management packs in an integrated development environment (IDE) that is similar to Visual Studio.
Note that the Service Manager Authoring Tool is only available for Service Manager 2016 and earlier versions. Starting with Service Manager 2019, management pack authoring is done using Visual Studio.
References: