It is impossible to completely imitate (La)TeX in Word. If you just want the font, then there is an OpenType version of Computer Modern, the default font of TeX. If you want the margins, just measure them on a LaTeX document and then set them in Word accordingly (I would recommend that you use KOMA Script or memoir as a base, not the default LaTeX classes, as the look imo better on A4 and letter paper.)

There is also a LaTeX template for Word. Since I don't own Word, I can't tell how good it looks.