Most of the world uses altitude in feet, and in the rest of the world pressure settings are given in hectopascals (hPa). 1013.25hPa = 29.92 inches. You may hear people reference millibars, but officially ICAO uses hPa. 1013 hPa = 1013 mb
Former Soviet Union countries utilize altitude in meters and China also gives altitudes in meters . There are conversion charts depending in which country you are flyingg, but you are given altitude in meters and you reference the chart and get the conversion in feet.

US registered aircraft still follow these procedures when flying in these countries.