Cu|Cu2+||Zn2+|Zn
H|H+||Mm?+|Mm

use similar salt in salt bridge at 1.5M to anticipate depletion of ion concentration in salt bridge. Usually, KNO3 is used.  

Use physics projection voltmeter (or Fluka meter) to show cell voltage. 
Hydrogen bubbling can be very slow - ~1 bubble per second or even a little slower.

Re-platinize Pt electrode if needed.