From Help:

To find all cells that have conditional formatting (conditional format:
A format, such as cell shading or font color, that Excel automatically
applies to cells if a specified condition is true.), click any cell.
To find cells that have conditional formatting settings identical to
the settings of a specific cell, click the specific cell.

On the Edit menu, click Go To.
Click Special.
Click Conditional formats.
Do one of the following:
To find cells with any conditional formatting, click All below Data
validation.

To find cells with identical conditional formats, click Same below Data
validation.