The most reliable fix is to ensure your ROM set version exactly matches your MAME executable version. For example, if you are running MAME 0.250, you should seek out a "MAME 0.250 ROM set".
In the world of MAME (Multiple Arcade Machine Emulator), games are not single files; they are "romsets" consisting of multiple data chips dumped into a compressed .zip archive. The file 463_mk3_ultimate.u64 is a specific data component—often a security or program chip—required for the emulator to recreate the original arcade hardware's logic.
If you have a "Split" or "Merged" romset, the emulator might expect certain files to be in a "parent" folder or a different ZIP file entirely.