There are a number of different ways the area of part of the drawing can be determined.
The area command (selected from the standard toolbar or started from the command area by typing AREA), sets a yellow shape over what can be quite complex areas. Entity snap tools can be used to precisely mark points on the perimeter of the area to be measured if precision is needed. The value for area will be reported in the command area in square units - mm square, m square or square feet depending on the base unit in use.
That value can be copied from the command area (use Control C combination), the single line text or leader command started and the value pasted into the text box. Round off the value to a suitable number of decimal places.
TIp: Turn off all entity snap operations while using this tool when trying to measure the area of complex garden beds as shown above.