how to add auto numbering in word table

How to Insert a Series of Numbers in a Microsoft Word Table : Microsoft Word Doc Tips.
How to Auto Insert Sequential Numbers in a MS Word Table | Automatic Numbering in Table Column
You can add auto numbering to a Word table using the built-in Numbering feature:  

Select the cells: Highlight the cells where you want to add numbering. To number the beginning of each row, select only the first column.  
Go to Numbering: On the Home tab, in the Paragraph group, click the Numbering button.  
Choose a format: Select the desired numbering format from the dropdown menu.  
Here are some additional tips:

To change the starting number: Right-click a number in the list, point to Numbering, click Set Numbering Value, and then enter the value that you want to start with.  
To continue numbering from a previous list: In the Set Numbering Value dialog box, click on "Continue from previous list".  
To use a different number format: Right-click a number in the list, point to Numbering, click Define New Number Format, and then select the options that you want.