Dear Aymen.
Obviously you dont like the numbers written to the lines in the plot.
OK. But remember: Mariusz already pointed out two websites where it is shown how you can make your own styles.
To give you an example ("quick and dirty"):
I define two frames by the number .2, a spacer by .05 and then a "binary code" with 0 and 0.1.
The first line gets the code 0 , meaning {0,0,0} or { frame, space, 0, space, 0, space, 0, frame}, the second code 1 and so on, the sixth line code 5 or { 1, 0, 1}. And I use a factor f to play around with the plots.
Altogether I define
f = .1;
d1 = f {.2, .05, 0, .05, 0, .05, 0, .05, .2};
d2 = f {.2, .05, .1, .05, 0, .05, 0, .05, .2};
d3 = f {.2, .05, 0, .05, .1, .05, 0, .05, .2};
d4 = f {.2, .05, 0, , 05, 0, .05, .1, .05, .2};
d5 = f {.2, .05, .1, .05, .1, .05, 0, .05, .2};
d6 = f {.2, .05, .1, .05, 0, .05, .1, .05, .2};
Now try (I had to eliminate some of your code because it doesn't work with my version Mma 7)
Plot[{B1[z], B2[z], B3[z], B4[z], B5[z], B6[z]}, {z, -0.3, 0.3},
AxesLabel -> {"z(mm)", "Magnetic Field at(Bo=0.01T)"},
AxesStyle -> Thick, PlotStyle -> Dashing /@ {d1, d2, d3, d4, d5, d6}]
Is it that what you wanted to see?
And of course you may modify the d's according to your own taste.