On mine there are two standard plugged opening like the one you would find on an auto, the top one is where you can adjust the brake shoe, looking in the hole you might be able to see the cog wheel that adjusts. Shortest route to know it's condition is to take it all apart, but a faster way if you know the brake has a good pad and if free of oil, you can disconnect drive shaft, with brake off you should be able to move the drum, tighten until it has some friction then back it off, reconnect the brake cable, drive shaft, lower to ground. My test was to put on a incline and see if it holds
If you decide to take the drum off, make sure you replace the rear seal of the transmission, disturbing a 20 yr old working seal it will leak on putting it back together
then you have to take it apart again, price of seal not worth the redo.
Disclaimer, do this at your risk:
You can do it with everything connected, jacking one rear wheel off ground, if you can turn rear wheel in neutral with brake off, adj brake pad until it locks wheel when brake is engaged, lower jack then do the incline test. Doing it this way you won't know the condition of brake shoes but you also won't disturb a whole lot of stuff.