Simplify the given expression. Enter your answer using only positive exponents.

6(n)3(m7)39n4(m)2n7=\displaystyle \frac{{-{6}{\left(-{n}\right)}^{{-{{3}}}}{\left({m}^{{7}}\right)}^{{3}}}}{{{9}{n}^{{-{{4}}}}{\left(-{m}\right)}^{{2}}{n}^{{-{{7}}}}}}=