convert each of the following:

. 155km to m
. 2.56Ml to l
.155uF to mF
. 1,850nm to mm
. 1.68Gb to Mb
. 165pm to nm

You must have been given a table or chart with the conversion factors between your different units.

Some of these I don't know.
e.g. what is pm and nm ?

the first is done this way:
1 km = 1000m
so 155 km = 1000(155) m = 155000 m