To Select an Unconstrained Hole, Using Feature Manager

Open the Feature Manager dialog from the Feature Modeling Primary Toolbox.
Click the remaining hole to display the solid with the hole feature highlighted in Feature Manager.
The feature that you click appears highlighted in Feature Manager. Previously constrained features have an asterisk (*) next to them. This helps to select the correct hole diameter when adding the constraint. When you construct a solid such as this, the number of the hole varies depending on the order in which the features were placed.