Can someone please explain to me how to use the 2MGFX tool. I want to convert custom effects written for XNA(dx9) so that they can work in my Monogame project. I am working with Monogame 3.2. Thanks in advance for the help!
Seeing how MonoGame builds its own effects can be a good starting point.
https://github.com/mono/MonoGame/tree/develop/MonoGame.Framework/Graphics/Effect/Resources
RebuildMGFX.bat call 2MGFX to build the .mgfxo files. Those files are then embedded as resourses build into the assemply/DLL.
In your case you might want to just include your shaders as content and load them as any other file. I think its also possible to compile them via the MGCB.
Some changes might be necessary to move your shaders to the new version.