Make sure that the headings in the document are formatted with custom styles. On the Format menu, click Bullets And Numbering, and then click the Outline Numbered tab. Click a number format. In the Level or the Preview box, click the heading level you want to number. For example, if you clicked 1 in the Level box, click My Style 1.
Repeat steps e through g for each heading style in the document.
Under List Numbers, select the Restart Numbering option. At under Number Format to be a specific number. Word will automatically continue the sequence from the number you inserted. On the Format menu, click Bullets And Numbering. Click the numbering style you used in the list that you want to continue.