Im trying to change my front and back wheel hubs from a 89' 325i and put some m3 e30 ones' but i dont know if i can use m3 e30 front and rear rotors(disc).Do i have to change calipers? or what.

a 325 has a 4 lug hub, M3s have a 5. So if you are changing the hub you have to change the rotor and mostlikely the calipers as well. I don't know if just changing the hubs to M3 ones will work as many 325 guys buy the whole M3 suspension to go to a 5 lug. Maybe you know something they don't. Besides the M3 lugs are very pricey- many M3 guys by the E28 5 series ones and swap the ABS ring to get the same hub at a lower price.