The usage of assets in mods for the game Skyrim.

Hello, I’ve been purchasing some 3d models from Fab and converting and turning them into mods for the game Skyrim for my own personal use. I was wondering if it was compliant for me to upload said mods onto the Nexus Modding website for Skyrim. The mods would not contain the raw original fbx or other format files, nor the raw original texture files. The mods would instead contain the converted files of those original files to make them work in Skyrim, so in this case, the raw fbx file would be converted into a nif file and be edited to make it work and look right in the game via other software such as blender, nifskope, and outfit studio. The raw texture png files would be converted into dds files and edited to make it work and look right in the game via other software such as substance painter. The mod would also be completely free and I would not make any money from the mod. The mod would be uploaded to the Nexus Modding website for others to download and use in their Skyrim game. The assets were purchased using the standard license, and I just need clarification and an answer to whether I can upload said mods to the Nexus Modding website, because this situation feels like a grey area. Also, would it be better to get direct permission from the author of the assets used?