psk/psa files

How can I tell which files are psk/psa?
Or what they look like.

There is no PSK/PSA support for Unreal Engine 4. Are you referring to UE3/UDK?

no I am not.
I just want to know what the files they support, like skins and other files like that
and how would I find them and can I change a skin file into a psk or a psa?
Thank you have a great day:)

do you mean skin like a weapon skin…ect?, and out of pure curiosity why would you want to change them to psk.psa?

I want to convert ut99 characters to ut4

But I want to know what files i need.