Using the relationship
log_b(x)=log_e(x)/log_e(b)
where there intermediate base "e" can be replaced with any other positive number.
log_3(43) (log 43 to base 3)
=log_e(43)/log_e(3)
= 3.761200/1.098612
= 3.423592...
= 3.424 (to the nearest thousandth)