[Iamyourfather]

Calculate the number of protons in a respiring liver mitochondrion, assuming its inner matrix compartment is a sphere of diameter 1.6 um.

Volume of the liver mitochondrion = ¾ π (0.75 x 10-3 mm) ^3 and [H+] = 2.0 x 10^-8 M
(1.33)(3.142)(0.75 x 10^-3 mm)^3 (2.0 x 10-8 mol/L) (6.023 x 10^23 protons/mol)/ ( mm^3/L) =

What do I divide it by? Explain.

[Yggdrasil]

One liter is defined as one cubic decimeter (1L = 1 dm³).

https://en.wikipedia.org/wiki/Liter

[Iamyourfather]

One liter is defined as one cubic decimeter (1L = 1 dm³).

https://en.wikipedia.org/wiki/Liter

But what am I supposed to be finding out?

From what you've said this is what I've done:

1 dm = 10 cm =100 mm
1dm3 = 100mm3

[Borek]

1 dm = 10 cm =100 mm

Yes.

1dm3 = 100mm3

No.

You have a cube of 10 cm by 10 cm by 10 cm, what is its volume?

[Iamyourfather]

1 dm = 10 cm =100 mm

Yes.

1dm3 = 100mm3

No.

You have a cube of 10 cm by 10 cm by 10 cm, what is its volume?

Ok. I need to find out how many mm3 are in a litre

so 1 dm = 100 mm
therefore, 1 dm3 = 1,000,000 mm3

[Borek]

therefore, 1 dm3 = 1,000,000 mm3

Yep.