What % of a molecule of glucose was made from Co2?

You do have a printed periodic table, right? You can get the information at www.chemicalelements.com/index.html but you really need your own printed copy to carry with you. It will be a primary reference for everything you do.

BTW it's CO2, not Co2. Spelling mistrakes are deadly in chemistry.

Atomic mass is the number in the upper left corner of each entry. So you add them up. For CO2 it would be:
C x 1 = 12.011
O x 2 = 31.9988
---------------------- ADD
........... 44.0098

Now do the same for the rest of the molecule and calculate the percentage.

Learn this process perfectly. There is a lot of it in chemistry.