Help with Optimizing and File Conversion of 3D Models

I am an Instructional Designer and I develop online learning experiences where I am looking to create some simulation/animations to put the learner in the right environment. I have found several models from 3D model sites Turbosquid and CGTrader that I would like to use for training I am developing...some of which I have already purchased and others I intend to purchase to have proper rights to. I have begun using iClone to build out some simple simulation/animations for our trainings to make them more engaging and interesting. But I'm having a hard time getting the models into iClone as props via 3DXchange and having them look the same as they do in their original 3D software, e.g. 3DS or Maya. I lose the textures and materials and I haven't had luck yet trying to apply them all myself...mainly because I barely know what I'm doing. This is mainly an issue on the bigger models where there are many objects and materials. I'm still very new at this all and I am simply not capable of doing it myself. I am looking for help in optimizing some of these 3d models so I can ultimately import them as props into iClone and maintain the textures and materials.