Problem with Top-Down game coordinates on mobile version.

My top-down map is located on XZ coordinates.
I need to read coordinates from touch on the map.
When i hit screen I get random constant Z coordinate and XY coordinates, wich always changing.
For example… I hit the screen(mpbile) and get
1)X: 123 Y: 436 Z: 1000
2)X: 345 Y: 326 Z: 1000
But I need
1)X: 345 Y: 1000 Z: 456
2)X: 375 Y: 1000 Z: 312
On the viewport i was doing these with mouse i have got only XZ coordinates changing, just what I need.

How do you get those coordinates? I want to get the coordinates when i touch the screen