You can change the format of the number in the numbered list:
–For all items of the same level.
–For one or more items of the same level. In this case, at the selected level, the list will split into two lists with different formats.
You can change the format of the number at any level of the list. You can specify a different format for each level.
To open the List settings window, which can be used to change the number format, follow the steps below:
1.Specify the required items in the list:
•If you want to change the number format for all items in the same level, place the cursor in any of these items or select these items without sub-items.
•If you want to change the number format for one or more items on the same level, select those items without sub-items.
2.Open the List settings window using one of the following methods:
•On the Home tab, in the Paragraph group, click the arrow to the right of the
Numbered list button and select List settings.
•Right-click to open the context menu and select the List settings command.
•When working in macOS, run the Format > List settings command from the command menu.
In the List settings window, in the Number format drop-down list, select the desired format. The first character of the selected format will be displayed in the box highlighted in the figure below. For example: if the number format 1, 2, 3... is selected, the box will display the value 1. If the No numbers format is selected, a dash will be displayed in the box.

If necessary, specify in the Text before box the text you want to display before the selected format character, and in the Text after box the text you want to display after the character. For example, if the list items should have the format Item 1), Item 2), and so forth, then in the Text before box specify the value Item, in the Text after box specify the value ).
When you select the No numbers format, filling in the Text before and/or Text after boxes is a prerequisite.
You can enter any characters in the Text before and Text after boxes, but no more than 15 characters in each box.
If you have selected a multi-level numbering for a list, where the first digit indicates the main level, the second digit indicates a subsection, and the third one indicates an item within that subsection (for example, 1.1.1.), then when you select any level other than the first one, you can only change the Number format of that level and the Text after (for example, change 1.1.1. to 1.1.A.)). The Text before box displays the format of the number of the previous levels of the list, and this value is not available for editing.

To save your changes, in the List settings window, click OK.