If salt had a density of 2.639g/cm3, what is the volume (cm6) of 1.00 lb. of salt?

Hi!!
Remember that if density is given V = M/D (always working with the
same set of units).
So here you must to convert lb to grams:
1.0lb = 453.6g
Now you must do a simple operation: 
V [cm3] = 453.6 [g] / 2.639 [g/cm3] = 171.88 [cm3]

The key of this question is the unit conversion, you have several
online tools to do this, I will give you one that shows how the
conversion was do, so you can learn to do it by yourself:
Unit Conversions
http://webphysics.ph.msstate.edu/units/index.html

(If you enter an integer like 100 add decimals -enter 100.00- in order
to obtain a more exact result, i.e. more significant digits will be
used, two zeros to use two significant digits in the conversion, etc).

Hope this helps you.

Your second question makes it clear that this is a homework problem.
To answer it, like your previous one, you have to understand the
relationship between mass, volume, and density. There is a very simple
formula relating these three factors, which you should be able to
figure out from my comment to your first question.

Hint for this question: convert lbs to g of salt.

I don't understand your comment. could you explain further?

Hello shelbyarps

I'm unclear why you are asking for an answer in cm6.  Volume is
measured in cm3 = cc= cubic centimetres.

The question is telling you how many grams of salt are present in 1
cc.  Convert this into a fraction of a pound, and then multiply by the
relevant number to calculate how many cc of salt go into 1 lb weight.