The jump to version 6.0 is rarely incremental. For hardware running on the P75-338 architecture, this firmware update likely introduced several pivotal changes aimed at modernizing the device.
If you need general steps for a (applicable to most devices): p75-338v6.0 firmware
Because firmware is hardware-specific and often proprietary, you should never download it from file-sharing sites. Safe sources include: The jump to version 6