How to get characters 3D models

To download characters 3D models, you can search for:

P3DM
The Models Resource
Search for Xnalara skins or XPS skin on Deviantart (requires a xnalara importer for 3DS Max or blender to open the model)
Search for MMD skins on Deviantart (requires a MMD importer for 3DS Max or blender to open the model)
Sketchfab

For unreal engine 4 and 5 games you can use the tool Umodel or Fmodel to extract the character and use ActorX import plugin to open on 3ds max. Some games requires a custom build of Umodel that you are able to find on the Umodel forums. Fmodel requires AES Key for some games and others, with .ucs/.utoc files requires a special .usmap file.
You also can extract models from games using tools like 3D Ripper DX or Ninja Ripper v1.7.1.
You can also search for specific tools made for that game that allow to get models form it. For exemple, to get character models from GTA IV you can use the tool OpenIV and open the models on 3DS max using GIMS IV. But keep in mind that most games do not have tools to extract models from them, so in most cases you will need to get your models using 3D Ripper DX or Ninja Ripper. Before trying to get the model from the game by yourself, search on google to be sure that the model is really not already avaliable. Xnalara skins are famous for covering a lot of types of game models, even models from obscure ps2 games, so there's a chance that the model you want, is indeed already avalible.