How do I find out how many acres this is?
I think you need more information. A standard shaped Section has 640 acres. Few people own an entire section. It is likely that you have a certain share of acreage within that section.
You need to find your deed or a probate document that has a description on it that will read something like “an undivided 1/8th interest in the SW4 of the NW4 of section 22-10N-5W”. From the description and the title opinions, the actual net acres can be determined. The original land patents were granted at statehood, but over the years they have been passed down through the generations and are usually much smaller interests now. That is called “fractionation”.