I have to use the given concentration of 7.03 micromoles/liters to determine the concentration for the following dilutions.

Question

1. mL stock solution-2
mL distilled water-8
2. mL stock solution-4
mL distilled water-6
3. mL stock solution-6
mL distilled water-4

Answer 1

You need to explain this a little better; I don't know what you're asking. I understand the 7.03 umol/L is what you have but I don't know what you're to do with it. What's the 2,8,4,6,6,4 mean?

Answer 2

I need to use those numbers to find the final concentrations for each individual solution.

Answer 3

You didn't explain anything. My assumption is that for #1 you are taking 2 mL of the stock solution and adding 8 mL distilled H2O and you want to know the concentration of the final solution when you start with that 2 mL of 7.03 umol/L. Again, I assume you want it in umol/L.
For #1 you have
7.03 umol/L x (2/10) = ?
For #2 you have
7.03 umol/L x (4/10) = ?
etc.
BTW, this works ONLY if the solution volumes are additive. Technically they are not but for such small concentrations you can assume they are.