The file you are looking for is part of a "split archive." For the firmware to extract correctly, you of the series (Part 1, Part 2, and Part 3).
To download and extract the firmware (specifically the "Starlight" version for 4K 3840x2160 resolution), follow this guide for handling multi-part archives and preparing the software for your smart board. 1. Download All Required Parts Download CV338H T50 3840x2160 Starlight part3 rar
Search for "CV338H-T50 3840x2160 Starlight firmware" on specialized forums like Lab-One Inside or electronic repair communities. The file you are looking for is part of a "split archive