Arduino and tachometer from 12V car battery gen

wich is the safest method to read the data

sry but i am not an engineer so my thoughts might be wrong

i also have some pcs of the above

tip35n NPN 25A
s8050 NPN 1.5A
irfz44n MOSFET 25A
1[ch925]5395
1[ch925]4007

thanks a lot