Extracting assets from other games is not impossible, but you may find that game developers are reluctant to tell you how or make it easy for you.
That's because even if you've purchased a copy of a game and customized your own character, the underlying mesh and texture data that character uses are the products of other peoples' artistic and technical labour.
Legally, the copyright or licensing rights for those assets are owned by the creators or their studio/publisher (depending on the details of the agreements involved)
So, if we tell you how to extract this data, we're potentially making it easy for less scrupulous visitors to this site to steal content that belongs to us and our fellow developers.
There may be reasons to use this data that are protected under "Fair Use," but we can't guarantee that anything we write here will be used only in this way.
I'd recommend checking into game modding forums if you'd like to explore this further, with a caution to please use your powers only for good. :)