You cannot read or write to a locked 2001 Mercedes ECU via the OBD2 port if the immobilizer is active. Page 1 provides the exact pinout for forcing the processor into (via the BDM or JTAG interface). You will need a programmer like the Kess v2, KTAG, or PCM Flash.
The "6.3" portion is critical. In tuning circles, "6.3" often denotes a specific or operating system (OS) revision for the ECM. For example, Bosch EDC15 or EDC16 controllers have version numbers. It could also refer to a file size (6.3 MB original dump) or a specific map pack number. Users on MHH AUTO frequently share these version numbers to differentiate between factory updates, stage tunes, or corrected checksum files.
Be polite and offer to share another file in return. The community is active but wary of "hit-and-run" users.