Copy the text you wish to replace or reformat and paste it into the "Find what" box in the replacement dialogue (Home/Editing/Replace, or Alt+E,E). Leaving your cursor there, click on the More button (lower left), then Format, then Font and select the characteristics (apparently, Bold) you wish to identify with the selected text.

If you are replacing it with nothing, leave the "Replace with" box blank. Othewise type or paste the desired text in that box and, if desired, choose formatting as before.

Does that solve your problem?