1 VA == 1 Volt Ampere == 1 Watt (Power = Voltage x Current) if you're in single phase (which you are) and you ignore efficiency and power conversion losses (which you can't). If you take the inefficiencies and conversions into account, you'll get something like 0.6 Watt for every VA. This is you maximum power draw. I hesitate to use analogies with you, because it proved
really ineffective with you the last time I did, but think of this as how big you can open your tap.
This does not speak to the power capacity of the battery in your UPS. This is typically measured in Ah (Ampere-hours) for UPS's, and mAh for power banks and cellphone batteries. Think of this as how big a dam your water tap is connected to, or more correctly, the amount of energy stored.
In order to get to kWh (Note that it's kiloWatt-hours, not kiloWatts
per hour, which is also a measure of energy), you'd time how long it takes (say 0.5 hours) to use your entire battery's power store (say, 10 Ah). Multiply this by the supply voltage, 220V (because Power P = Voltage V x Current A) and you get 1100 Wh, or 1.1kWh. Multiply by your local electricity cost in R/kWh to get your cost for 1 UPS worth of power.
To get your average power draw, take the kWh you got in the previous section, and divide by the time it took - 1.1kWh / 0.5 h = 2.2 kW. Which is
really high, but I did suck those numbers out of thin air, so that is to be expected