How to generate letters as attached

I think that this is the wrong approach. You should be using Mail Merge.

Your Data is in Excel which is good.

Open your Text File using Microsoft Merge.

Select the mailings tab and then select "Select Recipients" select use existing list and browse to select your data.

Then scroll through your letter and select all your data that appears in your database

Highlight the data, then Select the mailings tab and then select "Insert Merge Field"

Once you are done

Select the mailings tab and then select "Start Mail Merge"

Good Luck.