UV keeps unwrapping as a square

https://preview.redd.it/8don146hc8mh1.png?width=1913&format=png&auto=webp&s=fc97a68a0b781ba1786c63fe51987842b575d30c

this 3d model that I have edited keep unwrapping it's UV as a square and I want to know how to fix this (context this model is made form a mash up of other 3d models all of who have given permission for me to use at first I tried simply keeping a modifying the preexisting UVs but that did not work so I tried wiping the UVs to creat my own but then I realized I have zero idea what I am doing so now we're here)