Python - Cambiar elementos dentro de variables

n1=[1,2,3]

n2=[4,5,6]

n3=[7,8,9]

m=[n1,n2,n3]

i=0

a=0

for i,x in enumerate(m[a]):

    m[a][i]*=10

    print(i)

    a+=1

n1=[1,2,3]

n2=[4,5,6]

n3=[7,8,9]

m=[n1,n2,n3]

for i in range(len(m)):

    for j in range(len(m[i])):

        m[i][j]=m[i][j]*10

[[10, 20, 30], [40, 50, 60], [70, 80, 90]]