How do pilots manage metric altitude?
In areas where the ATC provides the altitude in meter (China (PRC), North Korea, and Russia), depending on the equipment (altimeter), the pilot can determine what to do:


In case of older aircraft, where the altimeter is calibrated in feet, the pilots use a conversion card for determining the altitude in feet, before dialing in the altitude to the autopilot.




Source: aerosavvy.com

Note: The conversion charts are standardized for the airspace and the pilots have to use it. For Chinese airspace refer FAA document on Chinese RVSM


In case of modern aircraft displays, the altimeter can be made to display altitude in imperial (feet) or metric (meter) units.