i had to redownload my game and i cant remember how i got GrimsMedievalCore_V_2_0_13 mod to work. now every time i try when i do see it on the loading screen it shows for two seconds with no music then forcibly closes with no warning.

"This is a script mod so you must install d3dx9_31.dll in your The Sims Medieval\Game\Bin folder"
When I installed Grims Medieval Core, I had a very similar issue because I was missing the .dll so I would double check that first.
For the mod location itself, you'll want to put it in C:\Program Files(x86)\Electronic Arts\The Sims Medieval\Mods\Packages. You may need to make your own mod folder.