(When using web sources, consult Microsoft’s official Visual Studio older downloads, Visual Studio 2012 Update documentation, and Visual Studio 2019 migration guides — use official Microsoft documentation and MSDN resources for authoritative steps.)
If you do not have a Visual Studio Subscription, you cannot legally download VS 2012 from Microsoft. In that case, consider: visual studio 2012 download microsoft 2021
Visual Studio Older Downloads - 2019, 2017, 2015 - Microsoft (When using web sources
Instead of hunting a 9+ year old IDE, open your legacy .sln file in (free). Microsoft’s project converters work well for C#, VB.NET, and C++ (with some toolset adjustments). This is safer and more productive. Visual Studio 2012 Update documentation