Choose the correct gene formula for each of the following on the Punnet Square

If she is a female heterozygote, she would be:

CcDd and here gametes would be

   C   c
D   CD   cD
d   Cd   cd

I understand the female portion, but the male I'm not sure how to determine the Genotype

No idea, a testcross is performed with a known genotype in this case the female is CcDd, with an unknown genotype, so we don't know what the male is.

What is the final answer for the four digit number?

Still need help on this

I'm finding it confusing too

In a test cross, the test subject is always recessive for both traits so that you can determine the which dominant traits are in the other animal being crossed (the female in this case).

So the male would have a genotype of ccdd.

The first row of alleles on the male side is cd because a purnett's square always starts with the first letter of the first genotype and the first letter of the second genotype. That's why the female's first allele on the graph is CD, because in her genotype, CcDd, C is the first letter of her Cc gene and D is the first letter of her Dd genotype. 

The second allele on the graph for the female labelled "alleles 1" would be Cd, as a purnett's square uses the first letter of the first genotype and the second letter of the second genotype in the second row.

Genotype three would be a cross between cd and cD which would result in a genotype of ccDd.

As a result, the number combination is:
Alleles 1 = 3
Alleles 2 = 1
Genotype 3 = 9
Test cross male parent: = 7