Kate, remember that you need to include the units as well!
For example you have a volume of
You may use a table to find the DENSITY of your material (basically how much stuff fits into a given volume of this stuff); these tables can be found in textbooks, websites...as for example:
Density tells you the amount of mass in grams that fits into a volume of
If you have
If you have different types of wood (cedar, fir, pine...etc) you can change the corresponding value of density and evaluate the new value of mass.