Approximately how many meters below the earth's surface is potable ground water found?

That very much depends on where you look.The depth at which stable water exists underground is called the water table (formally it is defined as the surface where water pressure is equal to atmospheric pressure). The distance you have to dig from the surface to reach the water table is called the depth-to-water.The depth-to-water varies tremendously; in some places you don't have to dig at all, and water bursts forth from the surface (0 meters); in others (mountains, typically) you may have to dig as far down as 400 meters. A more typical value is about 10 meters.
The water table can also change, and for a long time now water tables around the world have been getting lower and lower as people have drawn out more groundwater than is replenished by natural forces. If this trend continues, many places are going to run out of accessible groundwater, which will be very bad for the millions of people who depend upon wells for their drinking water.
https://www.usgs.gov/special-topic/water-science-school/science/groundwater-decline-and-depletion