You can't, but this is the best shot at it. The key to it all is Styles.
Understanding Styles in Microsoft Word
Tips for Understanding Styles in Word by Shauna Kelly
If your text is formatted using Styles rather than directly formatted, you should be able to tweak it fairly easily. If necessary, reapply the styles from the template after you insert the text into the new document.
If your text is formatted directly, i.e., you set the fonts, indents, etc. using those commands rather than Styles, you may want to paste as plain text and go through the pasted text and apply Styles after the fact.
If you haven't been using Styles for your formatting, better late than never.