I need to interpolate some data points. But I am not sure which kind of trend
line should I draw?

There appears to be many different kind..
I do not need a super fanciful one. My main purpose is really to find the
trend (literally) so which one should i use? Polynomial? and also how do i
know how many order? (what is a order anyway?) I am sorry to ask such stupid
questions, but i am a new beginner to advanced charts. I usually only need to
plot simple charts. and microsoft help is not as advanced for idiots like me
=p