Pages numbers are a property of page sequences, i.e. an explicitly bounded set of pages. All pages in the sequence share the same type and look of page numbers.
A sequence is associated to a page style which defines the geometry (margins and columns) and heading/footer characteristics.
Your first task is to define the various parts of your book. Usually you have a cover, some front material, perhaps a TOC, followed by the chapters. This implies four page styles (you can merge cover and front material if their layout and numbering is the same).
You will delimit the parts with a special page break. Insert>More Breaks>Manual Break pops up a dialog where you can choose the page style to activate after the break and reset the page number to any starting value.
You didn’t mention the save format. What is presented above is valid (and persistent) for .odt documents. If you save .doc(x), the concepts are very different and the cumulative conversion between DOC(X) and internal format will progressively damage the document structure, making next to impossible to fix the problems which inevitably happen.
Also, you didn’t describe how you format your book. With such a size, styling is mandatory IMHO. Otherwise tuning the look becomes an awful nightmare.
For more targeted advice, provide a few page sample of your document to evaluate your formatting skills.