These are the .vrca files obtained on VRChat.
Use this software to decompress these files and load them into Unity.
https://github.com/mafaca/UtinyRipper
example:
usr_73de6e2d-4a5e-4e0f-dd3a-604b36cb5b48 - avtr_e64d97ef-c28e-4701-9e96-02aa6e7f77c4
Player Name: xxxxxx
Avatar ID: avtr_e6dd97ef-c28e-4701-9e96-02aa6e4f77c4
Avatar Name: miko
Author ID: usr_6732bbf2-8363-4192-b70b-4b57a88c8330
Asset URL: https://api.vrchat.c...514e2d4a/2/file
Release Status: public
version: 6
Copy and use the Asset URL. The above items cannot be used. because this is samples.
Enter the name of the avatar with Ctrl + f and use it if it exists