How do I connect the pump to a digital input of the arduino?
can you offer a reason to do this ?
I think you will find a lot of post on here to show you how to connect your LM35 to an input.
and lots of post on how to control your pump with an output.
some friendly advise is to post a link to your devices. we know about the LM35, but a link to a data sheet would help others to find and reference things for you.
ditto anything on the pump.
is it a 3/4 hp 575 volt, 3 phase pump for the hot tub ?
or a 5 volt pump for the fish tank?
these things make a difference on how we can help.
but a huge THANK YOU for not using 'need help' as the subject !