If you search for "Themida 3.x Unpacker download," you will find two types of results: scam websites serving malware, or outdated tools for Themida 1.x.
: A static deobfuscation tool specifically designed to handle the mutation-based obfuscation found in Themida and Code Virtualizer 3.x. It has been tested up to version 3.1.9 . Themida 3.x Unpacker
There is no single "best" write-up for unpacking Themida 3.x because it is an extremely complex commercial protector that utilizes code virtualization If you search for "Themida 3
If you are attempting a manual unpack, you need to understand the anti-analysis layers first [6, 11]. Analysis of Oreans Themida Anti-Debugger Detections: A detailed write-up on Themida 3.x Unpacker