smooth ac to measure with dc voltmeter
Assuming the meter has a separate signal input, it's difficult to know without having the input impedance of the meter, but let's assume it's maybe 100K ohms or thereabouts. 

D1 and C1 (should be rated for 50V) filter the power to the meter. 
D2 (Schottky has a bit less drop, but you could use a regular diode too), C2 and R1
filter the signal to the meter. Again C2 should be rated for 50V (aluminum electrolytic). 

A suitable part for the capacitors would be a Nichicon UVZ1H471MHD. 







simulate this circuit &ndash; Schematic created using CircuitLab

The capacitor value is picked to have a time constant of about 1 second, which means that with 60Hz half-wave input, the ripple will be about +/-30mV or less than 1 count. 

Edit: Since you've got it separately powered, you can ignore D1 and C1. See edit below following comment by @EMFields on scaling so higher voltages can be displayed. I've chosen to scale it by a number that approximates RMS reading, taking into account the "approximately 100K" input impedance of the meters you purchased (as shown in your link). 







simulate this circuit

If we assume the voltage drop across the Schottky is 250mV then for 24VAC RMS we'd get a reading of 24.2V, and for 10VAC RMS we'd get a reading of 9.9V- pretty good for a simple AC-DC converter.