In the "Find what" box, type in chapter. Use the Format, Font control to specify the color and bold formatting. In the "Replace with" box, type in ^& and press Ctrl+E to specify centered alignment. Then click Replace All. (If you are worried about undesired effects, you could test first on a copy of the document.)

Note that the document you attached only contains a picture/screenshot of a page; it doesn't tell me anything about the formatting of your actual document.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional