Area of figure

[KseniaStrahova]

how to find area of rectangle? Is there any function to do it?

[DanPatterson]

Rectangle - Wikipedia

But I assume that it goes beyond this and you haven't seen the Shape_Area field in a featureclass table, assuming that you have one.

Perhaps you need to elaborate on your situation

[AndreasHall]

Here is one way to do it: How To: Calculate Geometry in ArcGIS Pro

[AlfredBaldenweck]

If you're just viewing your features on a map, I'm a big fan of the Measure Features tool, which is found on the Map tab of your ribbon.

Measure—ArcGIS Pro | Documentation

It lets you pick your units and everything, then shows you perimeter and area with just one click.