I'm not quite sure what you are asking. If you want to wire in a low resistance shunt that lets you use a voltmeter to measure amps, then you would normally buy a power resister, typically 0.1 ohms or less, that is rated for enough amps to handle the maximum load, wire it in series with the load & put a volt meter across it. Amps through a 0.1 ohm resister will be 10 times the voltage read across it. Amps through a .01 ohm resister would be 100 times the voltage across it. A 1 ohm resister would read amps to volts directly, but it would chew up a lot of energy & waste it as heat. Amps times volts = power in watts.
If you are buying
reading ammeter that uses a shunt, then the proper shunt should come with the meter when you buy it.
These days, inductive pick up ammeters are much more common than they used to be. They do not require direct attachment to the load. The cheap
ones only read AC. More expensive ones are frequently capable of reading AC or DC.