All parts must have the exact same name except for the "part#" suffix. Same folder: Place all parts in one directory.
Are you getting a when trying to open it? Do you have the other parts of the archive? PES _ POWER PATCH V1.part3.rar
If Part 3 is even 1MB smaller than the others (except the last part), the download is likely corrupted. All parts must have the exact same name